Angel(us) / Liam
Angel appears in the very first episode of Buffy. For the first few episodes, he keeps popping in, giving Buffy cryptic information and then disappearing. His true nature is revealed when he and Buffy share a kiss - he is a vampire, but a good vampire, a vampire with cursed a soul. Buffy and him try to keep away from each other, but their feelings are too strong and they eventually have sex. At peace for one second, Angel loses his soul and reverts into evil Angelus. He gans up with his old playmates Spike and , he torments Buffy and plans an Apocalypse. Buffy manages to stop him as Willow restores his soul, but Buffy must send him to hell to save the world.
Angel somehow returns six months later. Realising he can never give Buffy what she needs, he leaves for L.A.