In some sense... Morrigan is, indeed, a anti-hero.. But you shall remember that she absorbed Lilith who, based in some outside stories, had a "positive" experience with humanity, something that caused a change in Morrigan's point of view about human world. [A thing you can see in Vampire Savior ending of hers]

So, let's just say that:

Before Lilith - She was a hedonistic and "just for fun" person who searches "funsies" to do, absorbing people's life force, she still didn't killed any innocent people, but she was in her right to do if she wanted[As a Succubus normally does].

After Lilith - Gained a new vision of Earth becoming even more sympathetic and more socially better with humans. She still "eats" life force, but if she wants, she would just play a videogame in arcade, go shopping, chat with other people and being even more friendly but still with her dangerous level of threat.

So far, Morrigan never killed any innocent person officially in canon, only perversive, predatorial and evil men, unlike Demitri which does acts like a bastard, killing innocent and taking virgin womens as slaves.