was the Kai. Her heart was full of hatred and jealousy and she really cared for nobody or nothing except her ambitions. Granted, Dukat could be pretty bad, but he had true mental health issues and he did care about people, such as his daughter and even Kira.
That sadistically sexed up Mirror Kira! She was devious, depraved, debauched, and disgusting. She even killed Ferengis for sport. The Kai was corrupt. Mirror Kira was pond scum.
Worst as in most evil or worst as in least interesting? The Founders are the most destructive villains, so I'd go with them even if their motives are slightly more sympathetic than Dukat and Winn. Sure, they viewed their version of order as a preemptive strike against an inevitable decision to commit genocide against them. But they had no problems mass murdering billions of people just to make a point.
Winn was an excellent antagonist. She wielded her faith to justify her actions, was cunning and shrewd, believing that Bajor needed her guidance which only fuelled her ambition (which was a good mirror for how religious extremists really are very dangerous people, by the sway and grip they have over those that blindly follow). She also needed to deal with sharing the spotlight in the Bajoran faith with Sisko, as Kira comments what should've been her happiest day is tarnished by the fact the (non-Bajoran) Emissary is on the scene. She dipped a little in the middle of the series, when the PTB made her lighten up a little, but they quickly got her back on track. Louise Fletcher was absolutely wonderful in the role, taking a character that could've been such a moustache twirling villain and gave her depth in her own shallowness.
This is one of the great things about DS9. In no way was Kai Winn as evil as Gul Dukat, but the show did a great job framing someone who was basically space Hitler as a real and likeable person. Unfortunately, we often judge people more by their personality than by their deeds. The thing about Kai Winn is that her negative qualities are the type people tend to run into on a regular basis. Hypocrisy, sanctimoniousness, condescension, and petty abuses of power are things we've all experienced in real life and know how to hate, but most of us have never experienced forced labor or genocide. Since DS9, shows like The Sopranos, Mad Men, and Breaking Bad have dealt with this issue more explicitly. Their leading men do terrible things, but we like them because they're interesting, charismatic, and often behave how we'd like to behave. Just one more way DS9 was ahead of its time.
The main difference between Dukat and Winn was that Winn was from a set of circumstances where she could have never done the things Dukat did. Both of them were completely amoral demagogues that had no one's interest at heart but their own. It was fitting they wound up together. I didn't see Dukat as a Space Hitler so much as one using whatever system turned the Cardassians into these ultranationalist villains so long ago that it seemed natural to them, to his own advantage. He's like some SS beaurocratic officer, signing the bills for Zyklon-B canisters from Bayer, in his nice Hugo Boss SS uniform, knowing full well what he's doing but doing it because it improves his own station, not out of any real ideological feeling either way. He's no less a wicked character for it. At least in the end, Damar overcame his internal struggles and kinda did the right thing. In some ways Winn might have even been more potentially dangerous than Dukat. Dukhat had self destructive impulses and behaviors that the far more self disciplined Winn did not show until she fell for Dukat's honey trap. She managed to amass her power and intrigue without martial backing, without Federation approval, an appointed cleric with populist posturings in an angry wold that was rebuilding and might have become a serious power if it weren't for its strategic interest to the big powers of the age. The thorn in her side was that the prophets she would have used as props in her interpretation of her religion turned out to be actually real and their emissary was right down the hallway.
Sure you don't just like Dukat more than Winn? He did far worse things during his life than Kai Winn, and that's not all down to circumstance given the degree of power he wielded, even before becoming head of state. Feel like you're kinda making my point for me; while Dukat is a victim of circumstance, Winn is 'more potentially dangerous'. You're making excuses for things Dukat did do while denouncing Kai Winn for things she could have done.
Even at the finale I found Dukat more likable than Winn. Winn really did care about Bajor, and in the end she turned to The Emissary, but there's something endearing about Marc Alaimo. When Winn and Dukat were going at it, I wanted Dukat to win. "Are you still here?"
That's the thing. Ask me who I'd rather have to dinner or enjoy a few drinks with and it would be Gul Dukat all the way, just like I'd rather spend time with Tony Soprano, Walter White, or Don Draper than with Carmela Soprano, Skylar White, or Betty Draper (yes, I know these characters don't really compare with Kai Winn). At the end of the day we're far more likely to forgive people for bad deeds than bad personalities, but that doesn't make them better people.
It's not about liking. I like Winn's character very much actually. Everyone always loves villains, and she's wonderfully complicated. Dukhat got a little less interesting as the years rolled by. Mostly I just didn't care for the bajoran religion storylines. I just found them boring. I suspect a lot of people felt that way, and that didn't help acceptance of Winn's character.
I meant liking on a personal level. I don't think Dukat got less interesting as a character, but his storyline got muddled up during the finale.
Worst (but at the same time the best) villain was The Female Founder. A character with no qualms at all about genocide and murderer. Totally ice cold and ruthless I must admit that I really wanted to see that character killed off every time she showed up on the screen. Totally disgusting but a fascinating villain at the same time. I really liked Dukat and Winn as villains too. They were more "normal" villains than The female Founder but still great in their evil scemes. An extra point to Winn for looking like an old (and rather nice) aunt of mine. However, I wasn't that found of the Pah-Wraith thing. Too much demonology and mumbo-jumbo for me. Dukat and Winn were good as they were before season 7.
I've never seen even a few minutes of Sopranos, Breaking Bad or Mad Men, but I'll bet the premis of all of these shows could also be found in some plays from Shakespeare.
Gul Dukat was usually fun to watch. He had a great sense of irony and a little humor. He was bombastic and he knew it, but Kai Winn pompously took herself and her position too seriously to have much humor (if any). Dukat was probably the worst of the two, but the Kai might have come close or passed him in the future if she had had the chance.