Disclaimer: I do not own Ben 10 or Young Justice.
Ben 10: Ultimate Justice
-June 21, 2011-Original Ben 10 Universe-
Ben Tennyson sat on the last remaining skyscraper in Bellwood, think about what had just happened. Everything had gone by so fast, and Ben hadn't been able to anything.
A giant warship had appeared over Earth, and destroyed ever single human being on Earth with a blue laser. No one had been spared-except for Ben.
The only reason he was alive was because of the Ultimatrix. He was able to activate it and save himself, only to watch his family and friends be destroyed.
Now Ben was crying, because he knew this was the end of the world. He knew that only he survived the attack, and that nothing could bring back the human race.
He looked down at the ground 500 meters below. Then he made his decision, for there was no purpose left in the galaxy for him. He stood up, wiped his tears with his left arm, and jumped.
He flew straight down at the ground, going faster and faster. Then the Ultimatrix flashed and said "Galactic scan completed. Human race detected." Ben's eyes widened and before he knew he activated the Ultimatrix and slammed down on it. There was a green flash and immediately a blue flash right behind it.
-June 21, 2011-Young Justice Universe-
The team was in the mission briefing room which was now converted to be a training room. Superboy and Aqualad were sparing and of course Superboy had the upper hand. He slammed his fist into Aqualad's shield created from his Water-Bearers and Aqualad stepped backwards.
Suddenly, there was a blue flash at the ceiling and a vine like creature fell out. The entire team stopped whatever they were doing and stared at the strange creature. The creature then stood up and shouted "SWAMPFIRE!"
The alien had root like feet, mostly green with black on it sides, red spikes on its shoulders, red and yellow spikes on its head, green eyes, and a black and green hourglass symbol on its chest.
What is that thing? KD asked through the telepathy link. I do not know... Aqualad answered. Swampfire looked around and looked surprised. "Where am I?" he asked. "Wait... There's no more humans on Earth, so you must all be impostors!"
Swampfire ignited the methane in his palms and two fireballs appeared.
Kid Flash yelled, "RUN!"
Everyone scrambled for nonexistent cover as Swampfire threw barrage after barrage of fireballs at the team.
"Hold still, you alien scum." Swampfire growled as he missed everyone.
Kid Flash ran circles around Swampfire, who was in the middle of the room.
"Nah nah you can't catch me." KD taunted right as Swampfire threw a well placed shot that threw Kid Flash against the wall and he crumbled to the ground, unconscious.
"You will pay for that" Aqualad growled as he and Superboy charged Swampfire.
Aqualad took out his Water-Bearers and made them into swords. Superboy, who was faster, charged Swampfire and punched him-only to find his fist go right through Swampfire's stomach.
Swampfire grinned and said, "My turn."
Swampfire kneed Superboy's chin, which caused Superboy's head to snap upwards. Then Swampfire pulled Superboy's fist out of his stomach, threw him up, and punched him into the side of the room.
Aqualad took advantage of the distraction and cut off both of Swampfires' arms and was startled at this. The entire team also froze and stared at the two arms on the ground.
Swampfire turned around, chuckling. "You realize that won't help you at all." he said as two light green vines came out of the stubs of his arms and reattached the arms on the ground to Swampfire's body.
Swampfire then punched at Aqualad, who ducked instinctively and swung his swords at the Methanosian.
Swampfire threw up his arms to block the attack, but the swords cut right through them.
The arms re-grew instantly and Swampfire light his hands on fire and fired a column of fire at Aqualad.
Aqualad quickly morphed his swords into a shield, but the fire was getting uncomfortable for the Atlantean.
The rest of the team was busy helping KD and Superboy recover when Robin saw Aqualad was in trouble.
Robin ran toward the large vine creature and threw an explosive Batarang.
It lodged in Swampfire's stomach and detonated.
When the smoke cleared, the entire team saw that only the legs and lower torso remained of the vine like creature.
Suddenly, the vines started growing again and within seconds, Swampfire was normal again.
The team could only watched stunned as it said, "My turn." and smashed Aqualad into the far wall. Then it let loose a column of fire at the rest of the team.
Rocket, Zatana, and M'gann put up a shield to stop the fire but the heat was too much M'gann and she passed out.
"M'gann!" Artemis yelled, as she rushed over to her.
Robin jumped around the shield and charged Swampfire. Swampfire saw him and ceased firing and grabbed 3 spikes off his shoulders, which re-grew immediately.
He then threw the spikes at Robin, which then sprouted vines and grabbed Robin, keeping him occupied while Swampfire returned his attention to Rocket and Zantana, who were charging him.
They both threw discs of energy at him, but they simply went right through him or cut his arms or legs, which instantly re-grew. Swampfire then threw some fireballs at the two girls but they created shields to block it.
Swampfire said, "It seems we're at a standoff girls... OR NOT!"
He then hit the Ultimatrix symbol on his chest and four spikes popped out of it. Then the transformation began, and when it was finished, the result dumbfounded the girls and Robin.
"ULTIMATE SWAMPFIRE!" He bellowed out at everyone.
Ultimate Swampfire then proceeded to grab seeds off his back and throw them at the two girls in front of him.
The vines instantly captured Zantana but Rocket reacted faster and created a sphere shield around her. The vines attempted to break the shield, but to know avail.
Ultimate Swampfire then fired bombs at the shield, but the shield still didn't break.
Rocket then yelled to the creature, "You can't break this shield. It's powered by kinetic energy, so all the smashing and bashing will just power this shield forever!"
"Oh really" Ultimate Swampfire muttered when suddenly two batarangs sliced through his arms.
"Hey!" Ultimate Swampfire yelled in surprise. But before he could do anything, a small device landed in front of his feet and froze him.
"Ugh. I thought I would never get free of those vines." Robin said.
Ultimate Swampfire eyes widened as he saw that all the vines that were holding Robin had been disintegrated.
"Luckily I still had some acid to disintegrate the vines" Robin said with a smug smile. He walked up to the frozen Methanosian and said, "So what does it feel like being powerless now hmmm?"
Ben could only stare at the Boy Wonder in shock, trying to comprehend how this boy had defeated Ultimate Swampfire.