I'm not actually sure if I've an out-and-out evil character other than Plummy right now.
That's not to say that all these guys are likable...
Oh, I thought the Harlequinians were pretty evil. Evil does not necessarily have to do anything evil - that's probably a trope, too! ;)
Hey, I don't have an irrational bias against "ST:Voyager". I quite like it. But, in my defence, I do hate Neelix.
I'd argue that the Clownarchists are worse, but I'm biased. ;)
I watched the first season "Voyager" and then gave up. Granted, I did the same with "DS9" and then was told to give its reruns a chance over Spring Break 11 years ago, and came in right at the start of the Dominion Wars. I was hooked, though I'll wait for well-set reruns to see it again (or to luck into a cheap DVD set). It's more about the irrational banning - but also, keep in mind, that most of those banned would have little clue as to why they really were...
Sparta-dude totally earned his ban.