Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Nightmare Fuel: Birdy the Mighty
Tsutomu's death and some of the villains Birdy fights. Birdy's boss, who's a giant insectoid creature, might also count, not to mention her mentor who's a giant lizard with a face like a skull. There's also Violin's death and the events around it.
The entire Ryunka disaster at the end of the first season. Essentially anyone hit by it transforms into glass, shatters, and then melts.