Faith Lehane

In main continuity of the show, Faith is Initially a close friend to Buffy she gradually turns more violent & irresponsible with her Slayer powers, eventually killing a human man who working for mayor Wilkins, thinking he was a vampire. She at first denies then tries to frame Buffy for her own actions, eventually being cast out of the Scooby Gang & working with Mayor Wilkins in his evil plan for the ascension. They develop an oddly sweet father-daughter relationship. Faith poisons Angel, Buffy’s boyfriend, with a fatal poison to vampires that can only be cured by draining a slayer. Buffy almost kills Faith trying to subdue her in a fight and the dark slayer is left in a coma for a year. Awakening after Buffy has killed Wilkins and moved to college, Faith uses a relic left by Wilkins to switch bodies with Buffy and steal her life. Though Faith gradually becomes wracked with guilt as she lives Buffy’s life & experiences the connections she has. Faith saves a group of churchgoers from vampires and switches back with Buffy, then flees to Los Angeles. She tries to kill Angel again and tortures Wesley & knocks out Cordelia as revenge for failing her as a watcher. It becomes apparent Faith is actually trying to commit suicide by cop with Angel, but he refuses. She is put on a redemptive path being in prison till Angel loses his soul. Wesley convinced her to break out of prison and the two work together to restore his soul. After successfully doing so, Faith leaves for Sunnydale with Willow to aid in the fight against the first evil. She survives the destruction of Sunnydale & develops a complicated dynamic with Buffy and the Slayer organization.