Hermione Granger and the Power of the Atom
Dumbledore sat down and started the meeting. "Welcome, I've just received a message from the Gringotts, they've found and destroyed a horcrux in Lestrange's vault. They were pretty terrified that it might possess someone and cause a security breach. With the locket from Grimmauld and the Diadem from the Room destroyed and Harry's scar extracted, that means there's only Nagini and Voldemort himself left. What's the status on them, Severus?"
"Not good, Albus. Voldemort is protecting Nagini with everything he can. She's pretty much always locked up behind the defenses of the Manor. Even if I would destroy my cover to try to kill her I probably wouldn't succeed."
"Excuse me, but if both Voldemort and Nagini as well as all the high profile Death Eaters are at Malfoy Manor, couldn't we end the war if we destroyed it in?", Hermione asked.
"And how do you propose to do that, Granger? The Manor's defenses are ancient and comparable to Hogwarts. With Albus weakened, half the Order dead and Voldemort defending it, there's no way to take it. At least not while keeping Voldemort from fleeing with Nagini. I say we lure him out with a bait that's perfect for Nagini to assassinate."
"Your plan requires Harry, and he won't be able to leave the Infirmary for months. I know my plan sounds absurd, but what if we had a weapon that could destroy Malfoy Manor before they realize they're attacked? Wouldn't that work?"
Everyone in the room stared at Hermione.
"Are you saying that you have such a weapon, Miss Granger?", Dumbledore asked.
"Not right now, but I've been looking through the Alchemy books you've given me, and I think I found a method to make one. It'd probably take quite a bit of work and some exotic elements that I'd need your help with, but I think it's doable and according to my rough calculations it'd be absurdly powerful. More than enough to punch through the defenses of the Manor."
"And how would that weapon work, Miss Granger? Destroying such ancient protections takes quite a bit of power."
"The details are a bit complicated, but basically it'd abuse a trick in the transformation of one element into another to release energy. Severus would have to smuggle it inside, but it shouldn't be detected by any magical threat detection spells. Once it's inside and Severus has gotten out, we could remotely activate it."
"And it would kill the Dark Lord and Nagini, Granger?", Snape asked, no longer completely dismissing the idea.
"And everyone else inside and close by. It wouldn't be a very precise weapon."
"That sounds a lot like dark magic, Miss Granger", Dumbledore questioned, now looking worried.
"It's not!", Hermione defended. "Just some alchemy to prepare the exotic elements and a shrinking charm remotely activated through a protean."
"And it would kill everyone inside?"
"They're all Death Eaters!", Ron shouted.
"Voldemort also marked some children, not any older than yourself."
"The youngest Death Eaters are all in the Slytherin dorm, they won't be at the Manor when we'll attack."
"Alright", Dumbledore gave in. "I'll help you with the alchemy, Miss Granger, and if it works, we'll use it."
Snape arrived at the Order meeting in a hurry. "I've deposited the Device in my potion lab in the Manor a few days ago, it's set up and ready. There are currently no prisoners at the Manor and Narcissa is away too. I ordered all the elves on a long shopping trip. The Dark Lord and Nagini are confirmed inside. The only other current residents are the Lestranges, Dolohov, Avery and Pettigrew. I say we end it now."
"Good. Let's end this war.", Hermione said. "Let's do it. To the observation spot."
With a crack, Hermione, Ron, Dumbledore and Snape apparated to the hill a few miles away from the manor.
"Are you sure the muggles won't notice anything?", Hermione asked.
Dumbledore took out the Elder Wand and spoke a complicated incantation. "The entire area is hidden. The Malfoy's didn't want any muggles anywhere near their Manor."
"Perfect. Otherwise we couldn't do this. Ready?"
"Do it, Hermione!"
"Alright Granger, let's see what you got."
Hermione took out the protean-charmed counterpart to the activator. Removing all 3 safeties, one after the other. "This is it. Voldemort, this is what muggleborns can do!"
She placed her wand tip on the activator and pushed a bit of her magic into it.
In Snape's brewing room in the basement of the manor, the corresponding piece activated, triggering a prepared shrinking charm.
The shrinking charm imploded the small, subcritical sphere of alchemically enriched uranium to a fraction of its former size. Suddenly, each neutron from a splitting atom triggered on average more than one other fission, causing the amount of splitting atoms to grow exponentially.
E=mc did its thing.
A fraction of a second later, the four Order members only saw a flash of light as the ancient Malfoy Manor disintegrated in a massive fireball.
Voldemort's body and his horcrux had both been instantly vaporized from the gamma rays released from the nuclear explosion less than fifty feets away, and his soul lost its grasp on the mortal plane before he realized that something had happened.
As the shockwave safely washed over Dumbledore's shield charm, Hermione heard a sudden scream of pain.
"Severus! Professor Snape! Are you... Are you alright?"
"Ah, it's the Mark. He's gone. It's dissolving. It bloody hurt, but it's gone", he answered, teeth clenched.
"Are you sure it's not doing any serious harm?", Dumbledore asked.
"Yeah man, that sounded awful, we should get you to Madam Pomfrey!"
"I wasn't aware that you particularly cared for my wellbeing, Weasley."
"Hey, I mean you're not my favorite professor, but I don't want you dead, you're one of the good guys, one of us!"
"Well, thanks, I'm fine, the pain disappeared pretty quickly. Now, let's take a look at what's left of the Manor?"
The four looked at the smoldering crater where the manor had just been, surrounded by a burning mess that had, just seconds before, been a thriving forest. The mushroom cloud that had risen above overshadowed the scene, creating an apocalyptic impression.
After a short silence, Ron spoke up. "Hermione, don't you think you overdid it a little bit? I mean, the muggles shouldn't notice but the Ministry will!"
"That was only roughly half a kiloton, Ron. That's about as small as you can go with nuclear bombs. Muggles have ones thousands of times bigger."
"I don't think it would be a good decision to reveal what really happened... I guess we could probably create a story of a failed dark ritual", Dumbledore said. "Unless you want to be famous as the Girl-Who-Nuked, Miss Granger?"
"No, of course not, that would be ridiculous, although somewhat true I guess. Failed dark ritual sounds believable, and nobody knows enough about the kind of magic Voldemort used to notice anything. We definitely don't want others playing around with magical nukes. Let's summon and vanish all the radioactive waste before the aurors arrive, it should only be a few kilos. After that we return to Hogwarts. Harry will have a lot of questions."