Complex sentence: Angel was not only amoral and murderous as a vampire, but he was known to become obsessed with a woman, then enjoy torturing her by killing her friends and family.
Split into simpler sentences: Angel was not only amoral and murderous as a vampire, but was known to become obsessive and extravagently cruel. A recurring pleasure for him was the choosing of a vulnerable woman, whom he then tormented by killing her friends and family.