Angel (season 1)
At the end of the third season of "Buffy", the 242-year-old, re-ensouled vampire Angel left Sunnydale to give teenage Slayer Buffy Summers the chance to live a normal life. Angel is now living in the big city of Los Angeles. With Buffy gone Angel is now completely cut off from society, every day getting closer and closer to giving in to his vampiric hunger. It's not until he befriends the half demon and fellow Irishman Doyle, who is sent visions of people in trouble by The Powers That Be, and fellow Sunnydale resident Cordelia Chase, who grounds Angel's life in the humanity around him, that he truly begins to take charge of his life and seek atonement for his past sins. He sets up his own detective agency, Angel Investigations and begins to "help the helpless".
Spike (Buffy the Vampire Slayer)
Despite his apparent death at the end of "Buffy" final season, Spike returns in the fifth and final season of the spin-off series "Angel". Resurrected by the amulet in the Los Angeles branch of supernatural law firm Wolfram & Hart, he spends seven episodes as an incorporeal being akin to a ghost; he starts to understand being one when he battles "the Reaper" Matthias Pavayne. During this time he realizes he is being slowly pulled into hell. Later he becomes corporeal, due to a mysterious gift that arrives at the office of Wolfram and Hart. Soon afterward he is kidnapped by the psychotic Slayer Dana, who believes he was responsible for kidnapping and torturing her as a child. After this, Spike takes on Angel to prove which one of them is the Champion spoken of in the Shanshu Prophecy. Spike defeats Angel, but the prophecy remains ambiguous (the Cup of Torment is revealed as a fake containing Mountain Dew). Manipulated by Lindsey McDonald into "helping the helpless", Spike becomes a sort of rival to Angel; resembling the heroic Champion Angel was in earlier seasons before becoming disillusioned and corrupted by the bureaucracy of Wolfram & Hart. Cordelia comments on this strange turn of events after coming out of her coma in "You're Welcome", exclaiming to Angel, "Okay, Spike's a hero, and you're CEO of Hell, Incorporated. What freaking bizarro world did I wake up in?"