You have a bit of trauma, you always got yelled at and hit, no one was friendly or friends with you so you never learned to care properly, and you were always to one people would blame stuff on. In your spare time you would train hard, not stopping for much. You had some how ended up being an Avenger.

You and everyone else were on the mission, hydra agents coming at you from all directions, you absolutely plowed through them with your amazing fighting skills