Jack

"Turns out, mess with someone's head enough and you can turn a scared kid into an all powerful bitch."

Subject Zero is a human biotic and confirmed squad member. A young woman with a mysterious and violent past, she was once the subject of experiments that resulted in a enhancement of her biotic abilities; which had the added side effect of her unpredictable and fiery personality. This manifests itself in a lust for combat, a tendency to spout profanities and a body covered from head to toe in elaborate tattoos, marking kills and events in her life. She has run with various gangs and at one point was a cult member, keeping her head shaved after her departure. Subject Zero is described by Shepard as "dangerous, powerful and extremely violent." She is a potential (and notably blunt) romance interest for a male Shepard. 

Subject Zero is voiced by Courtenay Taylor.