Disney’s evil was always easy to see. The villians were beyond sympathy or understanding, and no need arose to find out why they were evil or what they really wanted. They were powerful and cruel. The women were beautiful: Maleficent, Snow White’s evil queen and Cinderella’s stepmother were gorgeous, but marked by  flaws of jealousy and amibition. The men were inept: Prince John and Edgar spring to mind. And there was Sher Kahn too, evil for ego’s sake. All were evil, plain and simple, end of story.

Nowadays it’s more complicated. The only thing necessary for the triumph of evil is for good men to do nothing is an adage that springs to mind this week, but I also think about Cormac McCarthy in Blood Meridian saying that "good needs careful tending whilst evil runs on forever of its own accord."

We are no longer in a position to accept such simple villians as Maleficent. Villians must, it seems, betray. They must betray their talents (by weakness or sin)  and also our heroes. Marvel Comics was great at origins of their villians, so much so that it became hard to tell good guys from bad.  This style is now common in cinema and animation.. The best recent example I know is Syndrome.
We see his origin (Mr. Incredible tells the cops "Make sure his Mom knows what he’s been doing") and, to a point, we sympathize with him. But for all his genius,
his craven attempts to get the public to like and admire him make him pathetic and,
despite his talents, beneath our affections. We almost sympathize, but not quite. He’s a good villian: complicated, cruel, self-centered, and even likable.

We need to see ourselves in our villians to be adequately betrayed by them.