Two of the most evil and two of the most beloved characters in the OUAT universe seem to suffer psychological problems.
Imo Cruella is a psychopath, because she was clearly born evil. She needed to kill someone in order to feel happy. After Isaac gave her power over animals and made her unable to kill, Cruella somehow gained a reputation and went to the EF, where she allied herself with Ursula and Maleficent. Making her unable to kill didn't stop her, as she probably expressed herself with torture.
On the other hand we have Zelena, a good girl at the beginning. Her negligent adoptive father and the knowledge of having a sister, who had everything she couldn't have (causing envy), turned her into a sociopath. Unlike Cruella she doesn't enjoy killing for sport, she just wants to make Regina suffer to get revenge and her happy ending and she will do whatever it takes to. It's very different, because the first lacks of moral and ethics. Zelena knows she's doing bad things. Cruella don't.
What are your thoughts about the insanity of the craziest Ouat characters?