Why?(Avengers x Abused!OC)

-got bored, went with this.-

There is a boy, his name is unknown to all but him. But he walks the streets of New York, hunting down everyone who was in the building that had killed him. He was killed 8 years ago by his father in an experiment where the boy was the lone survivor, said experiment were known as The Werewolf Experiments. He is now unable to feel any sort of pain, he has traits of a wolf, the senses and abilities of a wolf, and even a second form. These were all traits given to him after his death, all traits that made him absolutely deadly.

He's killed all but one of the scientists at this point, the one remaining is his father.

Of course a killer in New York City having killed 145 people already in all sorts of ways while leaving a trademark is NOT going to go unnoticed. So when the Avengers are brought in to bring him in, he might just cave. He never wanted to be a killer, but justice was not being served for his death and it angered him. So when the Avengers offer to get justice on his father for his cooperation what's he to do?

Oh yeah and that trademark he has when he kills? It's a simple question that no one knows the answer to.

Why?