Scar is the epitome of the Disney villain to me, but that's because I grew up on
The Lion King and it resonates just as much with me now as it did then. He's the archetypal villain—he's evil, petty, cruel, selfish, arrogant, and cowardly, completely lacking in redeeming qualities. But he's still ingenious, clever, manipulative, and strong in his own right, and creates a believably threatening force against the heroes. A story is really only as good as its conflict, and Scar presents a truly classic one.
Mother Gothel is also good, but for different reasons, because she represents something rather more visceral and personal to the audience than "evil uncle who wants to off you and your family and take place as regent"—she's an abusive parent. We see just how much damage has been inflicted on Rapunzel by this woman, both in the film and extracanonical material, and many people who have been in abusive situations have talked about how true-to-life she is. And seeing Rapunzel stand up to her and then her ultimate fate are both incredibly satisfying moments, and then seeing Rapunzel finding a true, loving family of her own and finding joy and fulfillment from the world she was always told was evil is a final kick in the teeth to what Gothel did to her, and it's wonderful that Gothel is such a compelling and emotion-inducing villain that we want to see that happen.
(Side note, but I'm really excited for the
Tangled animated series that's coming soon to Disney Channel, even if I do like Rapunzel's pixie cut instead of her long hair. Sort of a nice throwback to the
Aladdin TV series.)
Also, because I'm not sure if anyone's going to bring him up and I feel like I just have to, let us never forget
Fantasia's Chernabog. Because he's terrifying, powerful, and well-animated, and the music for his scene is just awesome.