Both of adaptations of IT when Pennywise uses his deadlights on the kids, ESPECIALLY in the new one where his spoiler. It's not pretty.

Also just rewatched Event Horizon last night and the way the titular ship messes with people's heads is fucking terrifying. A couple examples that standout include Justin's state of mind after being sucked into the core of the ship ("If you could see the things I've seen, you wouldn't try to stop me.") or how Peters gets vaguely hypnotized by the core to see her son running around, spoiler. And then there's what happens to Dr. Weir......