1. Brunt
What's worse than over the top stereotype Ferengi? The one dimensional antagonist to over the top stereotype Ferengi. And it's not Jeffrey Combs' fault, he was wonderful. You know the South Park character 'Scott, the Dick'? That was Brunt, only not a parody.
2. Vic Fontaine
Even the DS9 writers could not convince me that all these people would be obsessed with a holodeck recreation of a crooner stereotype. He is my biggest 'Netflix skip'
3. Alexander
Quarter human anti-warrior to incompetent idiot who suddenly wishes he could be a warrior. Ugh.
4. Late series Zek
I thought in his first appearance he was pretty good, but he became such a cartoon later on it's absurd.
5. Joran Dax
His episodes were always awkward, and he always seemed to me more like a bad guy on a crime procedural than a believable killer.
Dishonorable mention: The Intendant
Ooh, Alt-Kira is a lesbian hedonist, how ratings-interesting.
Why so much Winn hate? She didn't go downhill until the last ten episodes IMO. Until then she was the perfect politician. One of the most realistic villains in the series. I see Winn in the entire US senate.