Your an ex-experiment that was left to rot in a lab because you went wrong and was a danger to society. Your quirk was experimented on and therefore it became unstoppable. It got to the point where your barely human anymore

You sitting on the cold floor, strapped to the wall when you hear voices.

Shigiraki: Yelling from another room DABI! What'd you find?!

Dabi: Staring at you horrified Uhm....You're gonna wanna see this.

You hear footsteps coming into the room your in before they stop abruptly at the sight of you