Natalia Romanova (Earth-2326)

"I joined S.H.I.E.L.D. because I wanted to make amends for the things I did in the Red Room. But this... this is something bigger than me. Bigger than S.H.I.E.L.D. What do you need me to do?"

- Black Widow

Natasha Romanoff is a former KGB assassin turned S.H.I.E.L.D. agent who was assigned to hunt down Nick Fury after he went dark and started recruiting the Avengers. She was partnered with Hawkeye, and the two of them eventually discovered that the Avengers were fighting to prevent the Kree-Skrull War from decimating the Earth.