A Misunderstood Deku

The Butcher

Accepting that he was a liability, he smiled, placing all his bets on the vampire and the walking bomb. "Thanks... but be careful. I'd never forgive myself if any of my students were to fall to that monster!"

Izuku looked back at him, continuing to bare his teeth, plan in mind already. One that shouldn't put him in any real danger, as long as it went well. "I wouldn't plan on it!"

All For One finally managed to catch Bakugo. Enlarged hand gripping him with enough strength to keep him still... he asked, "Annoying child... you don't know anything about me, do you?"
Looking down, he knew his defeat... but still looked into his eyes. Or where they should be, grinning. "Well, I know one thing..."
Amused, the villain asked, curious on what his reputation has done for him, even now. "And what may that be?"
A different, more sinister voice spoke behind him. "That you'll be dead very soon." He was then immediately stabbed in the back twice, in both shoulders, with nearby debris. The Supervillain yelled in pain, flinging Bakugo away, into the ruins of buildings and trying to get the new assailant off his back. He tried a variety of attacks, from a variety of quirks, but to no avail. This attacker basically used him as a bucking bronco with nothing but two pieces of broken rebar.

Cursing, the man continued to state, alliterating his insults in as if the barrage would do anything: "You impudent, insolent, idiotic..."
Continuing to hang on, this new assailant merely asked, laughing madly in the chaos. "All your insults start with I... anything more... interesting than that?"
Noting the mental state of his attacker, All For One merely asked, "How about deranged?"

"That's a description that suits me fine!" Ripping out one of the blades, he put it to the supervillain's neck. Slowly slicing, he cut open, spilling his blood to the floor. Right after, Izuku also bit into his neck as well, taking in blood, and using... the more subtle effect of his quirk. Sure, All For One had a regeneration quirk, but it wasn't as effective, probably due to his previous fights, not to mention, age. Noting the slowdown in stamina and regeneration, the madman clicked his tongue before asking: "Aww... getting tired?"

He fell back, Izuku leaping off to avoid being pinned. AFO tried, but he couldn't move. For the first time in centuries... he was absolutely powerless. All his efforts couldn't lead to this. His body unresponsive, left to the mercy of a blood-crazed boy, as he looked up, with what visual quirks he had, up to a dark sky, with nothing visible save a news helicopter. His lungs rasping for breath against his failing body, his voice begged the killer to understand. "What have you done?!"
Walking into view, he stood over the villain, the carven smile terrifying in this context. He explained it for him, stating: "While my quirk isn't like most, it is versatile. My saliva has paralyzed you. Your regeneration is at its limit... and there is nobody but you and me..."

Recognizing the visage before him, the man's voice failed him. "Y-you... you're the Villain Killer..."

Kneeling down, the boy stated with an unnatural calmness. This was a once in a lifetime event for the serial killer, for someone whose goal was to kill villains... killing the first supervillain would certainly be a major accomplishment. And he was certainly eager to rub it in. "Your recent failures are all due to me. The USJ, The Summer Camp attack... their objectives failed because of me... and now, here you are. The leader of the League... all alone and... powerless..." He played with the knife, teasing the scars on his mouth as he watched the man, seeking signs of fear, became annoyed with the situation, as he was clearly suppressing those with a quirk right now. "You aren't afraid? Angry? Don't you feel anything?"

Putting on an air of confidence, the supervillain stated, "I have plans in place after my death. You cannot ruin those."
With a new objective now in mind, he asked, "Oh really? Well, I'll just have to do that then! But first, your smirk is annoying... how about we add something better. Something that Allmight taught me long ago!"

All for One realized what was happening, and tried his hardest to back away, but he was still paralyzed. Even though he could barely move his fingers, it wasn't enough. Allmight's biggest symbol, and his most annoying trait, was his smile... and this killer was renowned for his smile, now known by the villain to be self inflicted. If he was willing to do that to himself... "Stay away from me."

Leaning close, he was sure to be face to face with the ancient man, something that he didn't want. "Nonsense... it won't hurt... much..." giggling to himself, he examined the helm the supervillain wore. Gripping it, it cracked under his newfound strength, thanks to the experimental trigger Tomura had given him. Sure, it tripled his bloodlust as a start, causing him to go mad... but it also reinforced his strength, allowing him to break it with nothing but his hands. A fatal miscalculation. Hopefully his plan could work, and allow him to revive. At this point, it was his only hope. Izuku knelt next to the villain, not caring that news helicopters were shining lights down on him. Recording everything... While the heroes were helping Allmight and other civilians... they didn't dare get in the way here. This was both personal... and terrifying. He stabbed down both rebar into each shoulder, and then searched through his trench coat... before pulling out a pocket knife. "Can never have enough knives, to be entirely honest. Perfect for this, don't you agree?"

Putting the blade up to his mouth, Izuku carved a slow and deliberate smile into All For One, which regeneration made the process... more difficult. This meant more pain than was necessary, and causing actual screams from the old boogeyman. Then... the ravenette put him out of his misery by using the knife to rend his abdomen, digging through, and removing his heart. Holding it in a blood-soaked hand, he watched as it beat slower until it eventually stopped. AFO struggled to stay conscious, his body unable to regrow a whole heart and Izuku leaned over him so his face was the last he would ever see. The last words were a consolation, as he placed a hand on his now cut up cheek. Well, the bloodstained hand that still held his small pocket knife. If the man could cry, it was certain that he would, certainly if the moans of pain were anything to go by. It was naught but a whisper, but the vampire told him, "Hush... just go to sleep..." As soon as the words left his lips, the man's body finally gave out, and he died with nothing but scars and pain. When he was sure All for One was dead, the ravenette stood up and stretched, both hands still holding onto their contents... before casually looking down at the heart of AFO. With a satisfied grin, Izuku whispered to himself, "Finally, I grasp the old heart of evil in my hand... and now..." He crushed it. "It's time to find that new one... in Tomura Shigaraki."

No hero would approach him for the next hour, even as he put the knife away and tossed the heart aside. For the first time in Japanese history... nobody was sure if the battle's result was actually a good thing... and it was the first time the entirety of the country finally could put a face to the title... of the Villain Killer.

And, to their horror, he was still mostly free...