I have 3 answers. I played all those 3 games on my Amiga 500 Plus.
Prince of Persia. Lack of music is already creating an eerie atmosphere. But that screaming sound the main character makes when he falls down to his death traumatized me. And also the gore, of course.
Clive Barker’s Nightbreed: The Interactive Movie. Thank you, my ignorant parents, for making me play something labeled “Clive Barker” as a kid.
Qwak. The game is super cute but, those falling spikes!
What are yours?