This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Conception II: Children of the Seven Stars
Alec and Wake discuss the ramifications of what it feels like to have to kill a monster that, moments ago, was one of their friends and classmates and they didn't realize it until it was too late.
Even worse, for the majority of the game the characters have no clue as to what's causing people to turn into monsters and are afraid it could happen to any one at any time.
Worse yet, it nearly happens to Narika!
The healing process that Ellie and other Stillbloods have to endure every so often: Three days of endless, agonizing pain with absolutely no means of reprieve until it's all over. It's a miracle they manage to stay sane.
When Wake and Lucian confront the Original to rescue Ellie, he taunts them by talking about how he'll torture her and starts by blowing her face off!