Amen to Thor Damar! Klingons are simply stupid. "You have offended me. I fight you." They'd never get anywhere that way, always infighting. Cardassians were the closest to having a fascist vibe, too, which is a cool feel, even the way they stand.
Garak is my favorite Trek character ever, and I'd even nominate pre-Pagh Dukat as one of my top-3. When he gets into self-justifying mode, not only does he believe it, but if some of what he says is true, he actually did do some good, spare some Bajorans, while occupying them. Kira is unable to consider that. He is simply "bad" to her; this sets up one of the "good guys" (Kira) actually being morally blindered (a bit), though of course she had her reasons.
Post-ers have all commented on villain races. What about Vulcans?