Author's note: Despite reading a lot of YA novels, I am not especially fond of love triangles. From a shipper's POV, they're sort of fun, but ultimately, it's always obvious to me who the main character is going to end up with. There's a very basic pattern and formula. That being said, I thought it might be sort of fun to attempt to write one, if only once.
I'm not going to say I brought anything new or dismantled any cliches, but I thought I'd try to write it more how I think a love triangle would play out IRL; which is to say awkwardly.
This AU is partially based on FusionFall and I remember the two biggest ships (for Buttercup) were always Buttercup x Ace and Buttercup x Rex, so it felt natural to try to explore those both. As the story came along more and more, I realized I didn't know who I wanted to end up with whom. I had too many ideas and I didn't want to abandon any of them. So I came up with a solution: to write up a chapter solely for multiple, alternate endings.
I've thought hard and brainstormed ideas for what each of these six endings should be. I wanted to put a lot of time and effort into each of them so none of them seem like a forced afterthought and like they could each be a legitimate conclusion to Buttercup's love triangle and a legitimate conclusion to the story that's taken me two years to write. I want them each to feel real (for lack of a better phrase) and to satisfy my small audience and for them to feel like I put thought into whatever ship they were rooting for. I didn't want it feel like there was just one ending I really put work into and that that was the one I considered the "real" ending and the others were just scraps and half-thought, half-finished ideas.
I think I've rambled enough. This is probably the longest author's note ever. Enjoy the rest of the story.

Buttercup chooses Ace 1: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.
Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"The thing is, I really like and care about both of you and I know you both feel like that about me, but I don't feel about both of you in the exact same way.
"Rex, you're one of my oldest friends and we've been through a lot of battles together and when I was younger, I did like likeyou. A lot. You're really funny and nice an' you have good taste in comics. There isn't a day I don't think about the fun we had together and fighting with you side by side. But-and I know it's not your fault-you haven't been there for me in a long time. Not emotionally. Not when Mom died. Not when I lost my powers. Not when I got them back. We've hardly talked in years and now you just-expect to pick back up like normal. Like we're preteens again...it's not the same as it was. I'm not exactly the same either and you haven't been around me long enough to notice.
"You have been here for me now though. Through the Professor's cancer, you've been supportive and helpful and you've been a real friend to me and my sisters. You helped us capture our step-mom's killer. You've also been really jealous of Ace and my relationship when I'm not really sure you have a right to be...not after it's been so long since we hung out.
"Ace, you used to be my enemy for years. You broke my heart once before. But you changed...for me, because of something I wrote to you after...after Mom died. You changed and the Gangreen Gang changed. And you were good people all along. You just needed love and encouragement from people who really, really cared about you. You might not have been there with me in battle, but you were there for me when I needed you. You let me stay with you during...difficult times, you were there for me when I lost my powers, and when I got them back. We've been together through so much. You know me almost as well as Bubbles and Blossom and you really are a part of me and you're part of my family. I don't think I could've gotten through the last several years without you. You've been solid, you've been a constant in my life, and... I don't think I could ever feel the way I do with you about someone else.
"I love you, Ace D. Copular. Sometimes I think I love you more than I love myself."
Ace looked like he wanted to open his mouth to say something crude, but instead he stood up next to Buttercup. He was beaming. He realized he'd been paranoid about everything all along. Of course she loved him and he loved her. So he told her so.
"I understand. I'll always care about you, whether we're just friends or something else. If he ever hurts you or you change your mind, I'll be there." Rex told Buttercup.
"Thanks for being understanding. You'll always be my friend. I love you, just not in a romantic way." Buttercup replied.
Rex stood up and went back inside the house. There was still moving to be done and it would help him get his mind off everything.
"Buddacup, there's a few somethings I have to say to you, too. The Gang an' I have been talkin' an' we've been thinkin' 'bout maybe puttin' together a little band. No big deal, jus' a garage band fer now, after all we need all the practice we can get. An' well, I was wondering, would ya want ta be in it? The band that is?" Ace said after the other boy was gone.
"Hell yes! It's been awhile since I've played my bass, but I'm not too rusty!"
"And one other thing..."
Ace dropped down on one knee. It had been raining earlier and the porch was still damp, but he barely noticed. From the inside of his bulky jacket he pulled out a small box, the kind people only put jewelry in. He opened the lid, revealing a simple ring with a silver band and a pale green stone.
"Buddacup Utonium, will you marry me?"
She didn't say a word at first. Ace gulped.
This is it, I pushed my luck. Of course she wouldn't want to take things this far with a lowlife like me.
She cupped his cheek in her hand. Ace felt his pulse racing and knew Buttercup could hear it, too. Then she gave him a long, passionate kiss.
Ace didn't need to hear her say it; he knew what Buttercup's answer was.

Buttercup chooses Ace 2: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.
Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"Rex, you're one of my oldest friends and we've been through a lot of battles together and when I was younger, I did like like you. A lot. You're really funny and nice an' you have good taste in comics. There isn't a day I don't think about the fun we had together and fighting with you side by side. But-and I know it's not your fault-you haven't been there for me in a long time. Not emotionally. Not when Mom died. Not when I lost my powers. Not when I got them back. We've hardly talked in years and now you just-expect to pick back up like normal. Like we're preteens again...it's not the same as it was. I'm not exactly the same either and you haven't been around me long enough to notice.
"You have been here for me now though. Through the Professor's cancer, you've been supportive and helpful and you've been a real friend to me and my sisters. You helped us capture our step-mom's killer. You've also been really jealous of Ace and my relationship when I'm not really sure you have a right to be...not after it's been so long since we hung out. And I think you've been ignoring someone who really, really likes you...someone who even if you don't feel the same way about could use your support right now. Bubbles has a big crush on you and even if she didn't, she could use a friend to help her sort through things right now or at least listen to her. I don't think Blossom or me are the friends who are going to help her do that.
"Ace, you used to be my enemy for years. You broke my heart once before. But you changed...for me, because of something I wrote to you after...after Mom died. You changed and the Gangreen Gang changed. And you were good people all along. You just needed love and encouragement from people who really, really cared about you. You might not have been there with me in battle, but you were there for me when I needed you. You let me stay with you during...difficult times, you were there for me when I lost my powers, and when I got them back. We've been together through so much. You know me almost as well as Bubbles and Blossom and you really are a part of me and you're part of my family. I don't think I could've gotten through the last several years without you. You've been solid, you've been a constant in my life, and... I don't think I could ever feel the way I do with you about someone else.
"I love you, Ace D. Copular. Sometimes I think I love you more than I love myself."
Ace looked like he wanted to open his mouth to say something crude, but instead he stood up next to Buttercup. He was beaming. He realized he'd been paranoid about everything all along. Of course she loved him and he loved her. So he told her so.
"I understand. I'll always care about you, whether we're just friends or something else and I think for now we're good as friends. All this time we've spent together lately has stirred up a lot of old feelings, but that's what they are: old. I know Bubbles has feelings for me and I think maybe I have feelings for her, too." Rex told Buttercup.
"Thanks for being understanding. You'll always be my friend. I love you, just as a friend. Now, go, tell my sister how you feel." Buttercup replied.
Rex stood up and went back inside the house, pleased to have Buttercup's blessing. As he stepped back in, he saw Bubbles starting to head back to the moving truck to get more boxes.
"Hey, Bubbles! Wait up!" he called.
Back outside, Ace had something important to say to Buttercup."The Gang an' I have been talkin' an' we've been thinkin' 'bout maybe puttin' together a little band. No big deal, jus' a garage band fer now, after all we need all the practice we can get. An' well, I was wondering, would ya want ta be in it? The band that is?" Ace said after the other boy was gone.
"Hell yes! It's been awhile since I've played my bass, but I'm not too rusty!"
"And one other thing..."
Ace dropped down on one knee. It had been raining earlier and the porch was still damp, but he barely noticed. From the inside of his bulky jacket he pulled out a small box, the kind people only put jewelry in. He opened the lid, revealing a simple ring with a silver band and a pale green stone.
"Buddacup Utonium, will you marry me?"
She didn't say a word at first. Ace gulped.
This is it, I pushed my luck. Of course she wouldn't want to take things this far with a lowlife like me.
She cupped his cheek in her hand. Ace felt his pulse racing and knew Buttercup could hear it, too. Then she gave him a long, passionate kiss.
Ace didn't need to hear her say it; he knew what Buttercup's answer was.

Buttercup chooses Rex: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.
Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"The thing is, I really like and care about both of you and I know you both feel like that about me, but I don't feel about both of you in the exact same way.
"Ace, you used to be my enemy for years. You broke my heart once before. But you changed...for me, because of something I wrote to you after...after Mom died. You changed and the Gangreen Gang changed. And you were good people all along. You just needed love and encouragement from people who really, really cared about you. You might not have been there with me in battle, but you were there for me when I needed you. You let me stay with you during...difficult times, you were there for me when I lost my powers, and when I got them back. We've been together through so much. You know me almost as well as Bubbles and Blossom and you really are a part of me and you're part of my family. I don't think I could've gotten through the last several years without you. You've been solid, you've been a constant in my life, and... I do still care about you, but I feel like the feelings I used to have aren't as strong now as they used to be.
"Rex, you're one of my oldest friends and we've been through a lot of battles together and when I was younger, I did like likeyou. A lot. You're really funny and nice an' you have good taste in comics. There isn't a day I don't think about the fun we had together and fighting with you side by side. But-and I know it's not your fault-you haven't been there for me in a long time. Not emotionally. Not when Mom died. Not when I lost my powers. Not when I got them back. We've hardly talked in years and now you just-expect to pick back up like normal. Like we're preteens again...it's not the same as it was. I'm not exactly the same either and you haven't been around me long enough to notice.
"You have been here for me now though. Through the Professor's cancer, you've been supportive and helpful and you've been a real friend to me and my sisters. You helped us capture our step-mom's killer. And I've loved every minute of having you around again. It feels right. It feels like it should've been this way the entire time.
"I think I love you, Rex Salazar, if you'll have me."
Rex bolted up right. His heart was racing. Did I hear her right?
"Really? I thought there was no way! Buttercup, I love you, too!"
"Oh, I see. That's what I thought. I thought you were gettin' ready ta end things. I just wish things coulda ended differently." Ace said sadly.
"I'm sorry. I am. I just don't feel that way about you anymore. I still want to be your friend." Buttercup lamented.
"Yeah, you'll always mean a lot ta me. If things don't work out with Salazar, call me, okay? I'd like to maybe stay here a lil' bit longer, 'least 'til the boys find us an apartment, if that's okay with you and yer old man."
"Yeah, do what you need to." she nodded.
"Here's lookin' at you, kid." Ace tipped an imaginary fedora at them and went back inside the house. He had some unpacking to help with, before he started packing up his own things. Not that he'd brought much with him.
"So..." Rex said.
"So..." Buttercup echoed.
"What now?" the young EVO asked.
"Well, I was thinking..." Buttercup said. "We could go fly, maybe try an' find some bad guys to punch."
"Before we do that, there's something else I've been wanting to do."
He stood beside her and took her hands in his. He looked deeply into her large green eyes, brushed the hair out of her face, and leaned in for a kiss. It was a soft, slow kiss that seemed to last a long time, but was probably only a few seconds. They pulled away from one another slowly, reluctantly.
Buttercup was sure they both had big goofy grins on their faces.
"So you still want to go for a flight?" Rex asked teasingly.
"You know it." Buttercup said.
She took off into the air first. It took him longer, as he had to will his "wings" into existence, but he was soon hovering right next to her. Buttercup took his hand and they rocketed off into the heavens together.
They weren't gone long; they couldn't be. Rex, Six, and Doctor Holiday had to leave back for Providence any minute now.
They knew they wouldn't be able to see each other in person often, so they promised to call, video chat, or message each other every day.
Buttercup and Rex shared one last kiss before Providence agents arrived to bring him back.
He waved good-bye and winked at her as he stepped into the van. Buttercup waved back, if a little sadly. As the Providence vehicle drove away, Buttercup wondered when she'd see him next.
Buttercup chooses no one 1: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.

Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"Okay, so, you both like me and I care about both of you, but the thing is this whole "love triangle" or whatever has made me realize I want to take a break from dating for awhile. I want to focus on myself and my family for now. I've been in a relationship during the whole of my teens, I want to know what I'm like on my own.
"I want to help the Professor with his recovery and I need to make sure Bubbles is okay and that she feels like herself again. I went through a lot after Mom died and I had my sisters, my dad, and Ace to help me through it and so did she, but this...this is like she's living through it all over again. I need to make sure she gets through this, too.
"I'm sorry if I hurt your feelings. Maybe one day I'll be ready to be in a relationship with one of you, but not now."
They were quiet for a moment, then Ace spoke. "I'm not happy about it, but I understand. I'm sorry ' bout all the drama that this has caused. I'd like to maybe stay here a lil' bit longer, 'least 'til the boys find us an apartment, if that's okay with you and yer old man."
"Yeah, do what you need to." Buttercup felt sad breaking up such a long relationship, but she didn't regret it. This felt like the right decision.
"I'm sorry if I caused any drama either. It wasn't right of me to do when you were looking at losing your dad. I still want to be friends- you and your sisters, even Blossom, are some of my best friends." Rex said.
"Of course we're still friends. And I do love you both, just not in the way you want me to right now."
Buttercup awkwardly embraced them both and then all three went back into the house.
There was still moving to be done and things to be unpacked, after all.

Buttercup chooses no one 2: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.
Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"I care about both of you a lot and you care about me, but I don't think I should see either of you. After this whole "love triangle" thingy, I think I just want to take a break from dating and focus on myself and helping the Professor and Bubbles recover. Like you didn't do anything as creepy as though dudes in those After Midnight books Blossom liked during her goth phase, but I didn't like being pressured like that. It made me really uncomfortable and I felt guilty and weird about the whole thing."
"It's alright, Buddacup, I understand. I'll always be there for ya if ya need me. I hope you'll let me stay here a little longer 'til the boys find us a place ta stay in Citiesville." Ace said.
"Yeah, of course, I'm not kicking you ou- I mean, not really."
"I'm gonna head back in now, there's still unpacking to be done." Ace started for the door.
"Wait, Ace there's something I have to say to you." Rex said.
Ace was visibly surprised. "Yeah, what's that?"
"I think maybe we weren't still fighting over Buttercup- at least not the entire time. Maybe at first. I think after awhile we were just trying to goad or maybe even impress one another."
"Are youse sayin' what I think yer sayin', Salazar?" Ace frowned a little, but his tone was soft.
"Yeah, I mean, if you're interested... we could give it a try. If it doesn't work out or we don't like each other as much I think we do, we never have to go on a date again."
Ace paused a moment, considering Rex's offer. He'd never dated another guy, but he had thought about it. He'd always been afraid to though, because of the horrible things his father used to say about men who were with other men. It was the kind of fear that kept him afraid of being himself for years and years. He had been really surprised with himself that he'd been comfortable enough around Buttercup to tell her he was bi not long after they'd started dating. (It had taken him nearly a decade of being friends with the rest of the Gangreen Gang before he'd told them.)
"Yeah, I think I would like that, Salazar. I think I would."
Knowing they wouldn't see each other in person much, they exchanged contact information and then promptly went back to helping the others unpack.
Buttercup smiled to herself. She was glad at least one good thing had come of that silly love triangle.

Buttercup chooses both: Buttercup walked them both out to the back porch, where she hoped no one would burst in and eavesdrop. (It was a personal and private conversation after all.) She motioned for them both to sit on the big, heavily cushioned porch swing.
Buttercup looked at Ace, then Rex, then looked away. She bit her lower lip and repressed the urge to begin pacing. She was so, so sure of what she wanted to say; she didn't need to make it any harder by letting her nerves get the best of her.
Okay. Okay. You got this. Make like you're ripping off bandaid and do this fast.
"So, I think you both know why I brought you here. Um..." She trailed off.
She'd been thinking over and over about what to say and now she was already blanking.
Ace flashed a quick smile of encouragement. Rex mouthed "Go ahead."
Buttercup breathed in through her nose and exhaled violently though her mouth. She was sure she felt the porch shake around them.
"Okay, okay. Gimme a sec an' lemme...Lemme start over."
Buttercup took another deep breath. She wasn't used to being this nervous. Not ever in her whole life. When it came to fighting crime and saving the day, she was confident, calm, and cool, but when it came to emotions and love and everything that came with it, she was the exact opposite.
"Okay, so the thing is, you both like me and I like you both. A lot. You're both great, an' nice, an' cute and I don't if I could ever choose between you, because I love you both. I was thinking -and you don't have to say yes right now or ever even- that, um, I, well, uh, I want to be with both of you. Date both of you, I mean, if you're okay with."
They both just gawked at her for a moment.
"Uh, well, I didn't expect this to go over too well. Sorry for wasting your time, Rex, Ace." Buttercup hung her head.
Dammit. Dammit, what was I thinking? Of course they wouldn't go for it.
"Guess I'll just go. Uh, see ya later." she mumbled. She made to fly away, when Rex spoke "Wait, Buttercup!"
She floated back down and faced them again.
"I know Ace and I don't necessarily get along, but I'd be willing to work on that to be with you. So we can both be with," Rex corrected himself.
"Really! Ace...how do you feel about this?"
"Well..." Ace said, slowly and with a bit of hesitancy.
He took off his sunglasses and placed them on his lap, looking down the entire time. When Ace looked up again, he had a grin on his face and a twinkle in his eyes.
Is he really going for it?
"Well, B," Ace looked into Buttercup's eyes as he spoke, "I'm willin' ta give it a try, if this is what you really want."
"Yes! Yes, it is what I want."
Buttercup pulled them off their feet, embracing them both just a little too tightly. She hovered a few inches above the porch and twirled in the air, still holding her boyfriends in her arms.
She put them both back down. "Sorry, hope I didn't crush anyone."
"You can crush me an-" Ace started. Rex elbowed him.
Buttercup laughed. "Okay, we better get back inside or they'll miss us. There's still boxes to move, I think."
The three of them parted on better terms that day. They saw each other every opportunity they could and when they couldn't, they called or spoke on the over the internet. Things were still uneasy between Ace and Rex for awhile, but they did come to care for each as much as they cared for Buttercup and all three were very happy together.