Sasha Martin was a young teenager who was raised by her grandfather Holden Holliway after losing her parents during a shootout between gang robbers and police. As she grew up, Sasha had always been bullied a lot, causing her to gain a sense of vengeance over the people for doing her wrong. She somehow acquired an extraterrestrial gauntlet which granted her great power. Adopting the codename Southpaw, she used it to fight crime as a vigilante.
During the Avengers Civil War, Sasha Martin had been arrested by She-Hulk for her refusal in having herself register for the Sokovia Accords. She was imprisoned in the Big House and, facing the prospect of being remanded to the custody of her grandfather Holden Holliway, but was ultimately placed in the custody of hew lawyer Jennifer Walters. She somehow escaped from custody and joined the Dark Avengers.
Years later, Sasha had already retired and worked for the Goodman, Lieber, Kurtzberg & Holliway, working for her employer Jennifer Walters.