You joined the avengers from being young. Your parents and brother dead, killed in front of you to 'make everything simpler' 'one less thing to worry about' you had been tested on for years. Extreme supernatural healing along with strength of a god and speed of a cheater. It made you valuable to hydra. So they trained you to do the worst things, fear nothing and show no emotion. tony took you in like his own after storming a hydra base and a few years later you were trained like a badass assassin and one of the strongest avengers and you could use your strengths for good. After being with the avengers for four years or so. A young redhead assassin with a look that could kill. And she gave you something you had never had before. A reason to live.

they adopted you.