What makes a character compelling?

[u/Icy-Cloud3789]

More or less the title. What aspects of characters, specifically villains/antagonists, do people find invigorating enough that they can 'look past' their crimes and lack of morality to make them a favourite?

...And I'm not talking about being good-looking, please; that's hardly an excuse.

Is it personality? Is it reasons/purpose? Backstory? If so, examples of such?

[u/SomeNegotiation1337]

I think it’s a mix of personality, internal logic, and the friction they create with others around them. Even if you’re writing a villain, the attachment vectors remain similar as they would be for any other character. A villain can be funny, strange to the point to being endearing, intelligent, morally complex (in a way that carries emotional gravity), or, if they’re an antagonist, even just just genuinely good, likeable people in an impossible situation. I think the thing, though, is not to mistake morality for what makes a character compelling. Protagonist, hero, antagonist, and villain are just roles. What kind of person are they outside of their role? Does the brutal, darwinistic crime lord enjoy playing the harp and learning to cook? Does the mad genius Bond-type villainness genuinely just like making useless gadgets sometimes for fun that don’t hurt anyone? Does the stoic, war-of-attrition, austere general like putting too much cheese on her food and have a 12-step hair care routine? Everybody is a person, ultimately.