The thinking systems here that go in deciding what is sexy or not go like this (in my opinion):
Belief in one's worth and intensity/truthfulness of thoughts/emotions, manifested over time= Personal power = (because it implies a higher degree of being able to take care of oneself and knowing what oneself needs) Attractiveness, mental or physical, depending on how that is manifested:
Negative/positive. Individual learns to recycle negative stuff and use it to empower oneself, for the better or for the worse. This is attractive to those who think these people complete or help them on a personal or ideological level.
"Evil" nowdays can be both good and bad, unless we stay away as much as we can from political definitions and ideologies, and literally attribute evilness/meanness to "very wrong deeds and bad/abusive inclinations with other beings".
Feminine/Masculine.
When I see written "evil = sexy", i imagine a strong parallelism drawn to the image of the "sexy female goddess" that is impure and doesn't care about people, yet has an attractive way of presenting herself to gain followers.
Simply because people rarely link the image of an evil guy to sexiness. Am I wrong?
I find "evil" in English to be a funny word, because I just can't use it to refer to someone who is destructive or stupid/mean/undoing. It's like it has the connotation of being on the wrong side of the coin, but not because the Universe is a meanie, but because the environment they grew up in make such people exist and develop personal power. It's like wishing for collective bad actions to have no side effect. Ain't gonna happen. Everybody loves the evil element added to stories, it's what makes them enjoyable and epic, isn't it? Sometimes you cannot help but also admire the so-called "unfavoured" characters, and sometimes they make even more sense that the positive ones.
I have a strong tendency to criticise whatever "threatens me" or others before it can actually threaten or hurt me, but some people think these reactions are too strong. Then negative things happen to them while I'm perfectly fine, because they were too mellow and accepting. Evilness is a funny word. In some societies today and especially when holding a more important position, you're actually evil for thinking "no, how about you stop with crying about your gender and sexual orientation and thinking you need even more privileges, and use that money for trans/gay/whatever parades for a more useful cause, like to invest in Green Rooftops inside polluted cities?", basically telling someone to sort out their priorities, which is why i said the first step is to stay away from all the political interpretations that have always been changing and shifting, faster than the wind. OR, you can be evil for suggesting that the way people interpret a certain act or religion is incomplete or influences people negatively. Or you can be evil by killing toddlers for your own personal gain and grand scheme, but sparing some random other lives to give the illusion of mercy. Which is a more traditional interpretation. And everyone hates that kind of evil... how can you not indeed. How could we see all those stars during the night without the dark matter inbetween them?
I think I attribute the sexy evilness to Uranus actually. I might be making a distinction here between corrupted and evil though. Evil is more like where the energies manifest naturally. Corrupted is where it was weak enough and cracked to be taken by the evil.