YMMV / Battlestar Galactica

• Complete Monster:
  • Original series pilot "Saga of a Star World": The first Imperious Leader is the ruler of the Cylon Empire. Ostensibly drawing up a truce with the Twelve Colonies of Man with the help of Count Baltar, the Imperious Leader instead masterminds an attack on the Colonies, destroying their military and civilian populations, leaving billions dead across 12 planets. In an unpleasant touch, Imperious Leader has the jamming lifted just in time so the crew of the battlestar Galactica is Forced to Watch their civilization be destroyed. Learning of the escape of many survivors, the Imperious Leader orders the extermination of whoever was unlucky enough to be left behind. When the refugees protected by the Galactica land on the planet Carillon, the Imperious Leader draws up a plan to destroy the warship and leave the rest of the humans to be fed on by his allies the Ovions before he's destroyed.
  • 2003 series:
    • Brother John Cavil, aka Number One, is the de facto leader of the Cylons, and the first model of the Significant Eight made by the Final Five, the progenitors of the race. Angered by his creators' decision to give him a human body, Cavil kills his brother Daniel out of jealousy, wiping out the line before wiping the minds of his five parents and placing them on the Twelve Colonies. Cavil then initiates a nuclear holocaust against the human worlds, killing most of humanity, and then afterwards spearheads the campaign to kill the survivors, killing a young orphan boy just because they were becoming friends. When his siblings vote for peace with humanity, Cavil perverts it by enslaving them on New Caprica, using a Scarpia Ultimatum to rape his mother, Ellen Tigh, while torturing and mutilating his father, Saul Tigh. As information on the Final Five is discovered, Cavil reacts by permanently boxing the Threes and lobotomizing the Raiders, wiping out the Sixes, Twos, and Eights when they object, leaving only a handful alive. When the Resurrection Hub is destroyed, Cavil kidnaps and tries to dissect little Hera Agathon to uncover the secret to Cylon resurrection. While John claims he wants to be a robot more than anything, he willfully succumbs to the lowest human instincts he so hates: vengeance, lust, and sadism.
    • "Black Market": Phelan, the ex-military mercenary turned crime lord, runs the titular market, which includes a child prostitution ring. Having Jack Fisk murdered for trying to get more compensation, when investigated by Lee Adama, Phelan kidnaps Shevan and her daughter Paya. Selling the latter into the ring, Phelan threatens to cut up the former in an attempt to get Lee to back down.