Most characters in TV have a device inside them that makes them either "good" or "evil". Gul Dukat is one of those delicious characters whose device is defective.
Dukat started off as a Kirk-like equivalent in the brutal Kardashian expansionist military regime. When DeepSpaceNineLand was known as "TerokNorLand", he was the general manager and colonial overseer of planet Bajor. His job involved keeping the "lesser peoples" under his "protection" from harming those that would take their world from them. Dukat ruled the Bajorans, who themselves were a nice enough group of folks for a bunch of space hippies, with a combination iron fist and genuine concern for their well-being.
As far as the viewer can be certain, Bajoran occupation was made far more humane under Dukat, which is a good thing as far as it goes, I guess. But it is shown beyond the shadow of a doubt that the man brutalized, killed, and raped numerous Bajorans directly or through decree. And it isn't like Dukat was exactly in the business of making sure all the Bajorans got free health care and an excellent postal system under spoonhead rule. To be fair, many of his people in his position would have been far less kind to the Bajorans without any concern for them. So we can call Dukat's regime of torture and plunder something that shows he is a somewhat good-hearted and kind man. I have no idea how that just made sense, but fuck me it did.
Later he became a pirate fighting Klingons with a stolen Bird of Prey which elevated him to the realm of "awesome". So awesome in fact, the people he used to oppress for a paycheck let him use their space station and supplied him free of charge.