Angel: I did a lot of unconscionable things when I became a vampire. Drusilla was the worst. She was...an obsession of mine. She was pure, and sweet and chaste.
Buffy: You made her a vampire.
Angel: First I made her insane. Killed everyone she loved, visited every mental torture on her I could devise. She eventually fled to a convent, and on the day she took her holy orders, I turned her into a demon.