The central question informing the character of Angel is asked during season 3, first in the episode “Amends.” Angel’s been having really bad dreams. Except they’re also teh sexy and over-the-top with all the blood and pain and dying and the—wait for it—decadence of Angel’s sordid past. So a suicidal and tormented Angel asks Buffy (BtVS, season three, “Amends”), “Am I a thing worth saving, huh? Am I a righteous man?
You can read MacAllister’s response in this introduction to a series of re-watching Joss Whedon’s Angel.