This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / UFO Robo Grendizer
In the Go Nagai manga, the scenes of genocide in the planet Fleed. Especially the scenes involving Barados. Not only he deliberately targeted women and children to exterminate the Fleedian race, but also he captured hundred of children and dropped them from a height from three kilometers. Duke states it was like "a deluge of children".
Lord/Lady Gandal is a BaronAshuraExpy with two personalities, a male one and a female one. During the first season, his body was male, but when the female side wanted taking control, his face split in two halves, revealing a tiny female human inside the head.