And I agree with all of those who find Damar hot hot hot as well - and with those who would find Dukat sexy were he not chillingly corrupt, self-centered and just downright nasty. Props to Marc Alaimo for bringing all that out.
I can see how people might find some characters too evil to be sexy... In fact, I've felt the same way a lot of times. There are some characters who are just so evil, creepy and one-dimensional, without any redeeming characteristics, that I really can't find them sexy, however good-looking the actor is, and whatever he's like in RL or other roles. And then there are other bad guys that throw you for a loop by exhibiting some appealing qualities, some humanity, mixed with all the awful stuff, so you kinda hate them and love them at the same time. It's only then that the illicit lust kicks in.
But the line between "I really don't find this guy attractive because he's such a creep" and "I really shouldn't find this guy attractive, but I do" is probably different from everyone. For instance, I was puzzled how some
Lost fans could find Keamy hot - yeah, OK, he is tall, well-built etc. but one-dimensional mercenaries are really not people I can think of that way. Or, for instance, I never found Angelus on
Buffy the least bit attractive, because he was such a totally cruel asshole, even though Angel was attractive - even though I know that some people felt differently and thought he was hot with his leather pants and badness, yada yada. While on the other hand, Spike at his most evil (think early-mid season 2) always somehow managed to be sexy and charming and sort of lovable - even though he was menacing, violent and predatory, he had those traces of humanity, like his love for Drusilla, his sense of humor and his somewhat boyish rebellious attitude. And then for an extreme opposite example, in season 7 there was a villain played by Nathan Fillion, who was so incredibly creepy and evil <shudder> that I don't think even the biggest Captain Mal fans could find that guy hot at all. Or, another example -
Oz - I found the characters of Ryan O'Reilly and Chris Keller sexy despite being ruthless manipulative killers (well, most characters on that show were sociopaths and killers...), while I found Adebisi (although a great character) too repugnant even to notice that the actor was very good-looking - I only noticed it when the character went through a slightly more emotional and soul-searching phase at the end of season 2 when you kinda felt sorry for him. (Only for a while.)
When it comes to Dukat, I have to say that, for me, he falls into the second camp, for most of the show. As played by Marc Alaimo, he always walked that tight line and managed to be charismatic and human (!) enough, with his occasional heroic moments, his love for Ziyal, his attempts to get Kira and Sisko to like him, and even with his narcissism at times when it was treated humorously. He was such an engaging character because you often thought he could be a good man, perhaps...and then it was all the worse when he turned out to be even worse than you previously thought, but for the most part, he was ambiguous enough that you couldn't quite hate him 100% without liking him a little.
Except in the last episode when he got possessed by the Pah-wraith and went all cartoon villainy. I didn't find him attractive at all in that scene.