One of the most awesome villains in all of Trek is the former overseer of the ore mines on Terok Nor from Cardassia Prime called Gul Dukat.
Dukat saw himself as the long suffering do-gooder who went out of his way to make the Bajoran slave laborers more appreciative of him. But what thanks did he get?
Always striving to be liked by one of his nemesis on the former Terok Nor (now Deep Space 9) named Kira Nerys, he more often than not missed his mark and just ended up pissing her off.
In a classic moment, Dukat boards DS9 with the good intentions of helping the crew stop an auto destruct sequence--but only in exchange for a permanent presence back on the station. Kira is having none of it. In "Civil Defense," he attempts to leave and return in time to shut off the lasers that are tearing through the station in order to give Kira enough time to change her mind.
There's just one hitch---his attempt to leave activates another part of the auto destruct. He's prevented from leaving and told by the automated voice recording that he's bound to stay on the station and die like a man rather than take off in an act of cowardliness.
After having regained a powerful position in the newly formed Cardassian government, he brokers a peace treaty with the Dominion in exchange for their protection and influence in the Alpha Quadrant.
He eventually goes insane after the death of his daughter and ends up on a spiritual quest to find a way to absolve himself of his resentment and self-pity by teaming up with a wormhole entity---the arch enemies of the prophets called the Pah-Wraiths. His primary goal is to destroy those ungrateful Bajorans once and for all!
Later, Dukat goes to a plastic surgeon to be made into a Bajoran. He then visits the egotistical and power hungry spiritual leader of Bajor, Kai Winn.
Winn, like Dukat, craves admiration and respect and will even sabotage her own people's best interest to get it. We learn early on that one way she does this is to use her influence on a devotee to get her to assassinate a rival for the position of Kai. This attempt fails but she is later nonetheless made Kai with the help of another power hungry politician named Jaro who himself is hellbent on taking over the government. Winn betrays him when the truth about their alliance is about to become public knowledge.
Winn and Dukat end up joining forces through the influence of the Pah-Wraiths. At first, Winn assumes Dukat, disguised as a Bajoran farmer, is sent by the prophets to usher in a new era for Bajor.
That's true, but not in the way she thinks. She freaks out when her aid reveals Dukat's true identity but Dukat uses his gift of persuasion to convince her the prophets have done nothing for her or for Bajor. The Pah-Wraiths will giver her the power she desires in exchange for her allegiance.
She takes the bait but meets her fate when the two ill-fated megalomaniacs conjure up the evil spirits in the fire caves. Winn's greatest adversary, Bajor's Emissary Ben Sisko, shows up to stop the fiery ghosts from burning Bajor to a crisp. Winn is eaten by the fire and Dukat, possessed by the Pahs, is consumed by fire after he and Sisko exchange fisticuffs and go sailing off the edge of a cliff.
The Pah-Wraiths are contained in their fiery prison in the caves.