I do have a friend who does only date assholes, it's very sad and she says so. They have done things like break her arm, break into her house after they'd broken up and steal all of her knives etc. It's actually a repeated pattern in her relationships that strikes me as pathological.

Yeah that's the thing, you don't have to give into the incel mindset to notice this kind pattern.

That said, the incel/"nice guy" vibe is defining asshole as "someone who is more confident than me".

Yeah, although I do think that the "asshole" and the "nice guy" are two sides of the same coin (both toxic but in different ways; one more overt and the other covert). Actual confident/good guys often get mistaken as "assholes" simply cuz they have the confidence, like you said.