Unyielding

Hidden Power

3rd POV

A thick black smoke encompasses Y/N. It hits the ground immediately stripping it of life. His jacket begin shriveling up and erodes to dust. The Nomu finally begins succumbing to the corrosive smoke leaking from Y/N. It's hand is broken down as each layer of its arm is peeled away.

Uraraka: "I'm scared. What's happening?"

Toru: "I don't know."

Mineta: "Deku?"

Deku: "It's just a theory. But something tells me that smoke around Y/N is super corrosive. It seems to eat away at everything it touches."

Iida: "To think he was hiding something like that."

Yuga: "I'm just glad he's on our side."

Unknown to everyone this was the full extent of Y/N's quirk. While being able to walk off mortal injuries that's only a portion of his power. By forgoing all forms of control his body releases a powerful smoke that kills anything unfortunate enough to fall in its path. But this kinda power is a double edged sword.

Y/N: "Time to kill."

Blood leaks from his mouth but he remains unfazed. He delivers a left hook that embeds itself into the Nomu's side. Its flesh is eaten creating a wound that gushes out blood. Y/N kicks the Nomu's knee instantly eating it away entirely. 

On the ground Y/N grabs its face smiling like a madman. He exhales expelling that smoke in the Nomu's face. It screeches as its entire body is broken down from blood to dust. When it fully dissolves Y/N looks at Shigaraki.

Shigaraki: "You've got power. Come join us."

He holds out his hand. The heroes of UA finally arrive forcing Shigaraki to retreat.

Shigaraki: "You haven't seen the last of me."

He leaves with aid of Kuroguri's portal quirk. Meanwhile All Might and other heroes walk to Y/N. 

All Might: "Alright Y/N. Time to power down."

He grabs his head screaming in pain. His past clouds his mind making the smoke build in intensity. His shirt crumbles to dust. This reveals his body to be cracking and splitting open. This' the drawback of his quirk.

He screams rushing at All Might. Midnight rips her costume sending her pheromones at Y/N. He stops coughing. But his quirk quickly burns away the scent while eating up the ground. Midnight's pheromones are consumed with Y/N's quirk turning on her. She screams as her exposed arm begins blistering.

Y/N: "Death claims all!!!!"

Snipe fires his gun at Y/N. His body is struck but his wounds begin leaking blood a gallon a minute. 

All Might: "Stop you'll only kill him!"

Ectoplasm: "Well we gotta find some way to stop him!"

Cementoss places his hand on the ground. A massive stone pillar erupts hitting Y/N in his face. His face is cracked open making his smoke dissolve into the air. Everyone sighs in relief as All Might picks him up. They all look at Y/N as his wounds continue to bleed.

Snipe: "What're we gonna do with him?"

Nezu: "Get him to a doctor."

They all look at him in shock.

Ectoplasm: "You can't be serious."

Nezu: "Deadly."

Cementoss: "Why?"

Nezu: "He easily took out an unknown villain that nearly killed Aizawa. I fear if he wasn't here then we'd have a tragedy on our hands."

Snipe: "But he's a massive liability."

Nezu: "He's just a little troubled. He's likely been through more than anyone here."

He looks at Y/N as his bleeding starts slowing down.

Nezu: "We take care of our students. No matter what. And as your superior I order you all to help this child."

Though reluctant they all nod. 

Nezu: "Get him out of here."

All Might: "Right away."

He leaps away. Meanwhile in Y/N's mind we see him thinking about the past. More specifically the day his life started to go down hill.