I rank them on how well they help move the story along, How well they fit their role, and how interesting they are to watch. N isn't innocent either, yet we still love him. Cyn just does it bigger.
You misunderstand me. I'm not saying that she's not evil. She's hella evil. But she's entertaining. She's interesting. And that's why I say she's a good character. She keeps the story worth watching, as a good villain should.