Disturbing spell idea, is there already one like it?

Is there a spell that makes an evil creature feel all the pain they've caused others throughout their life at once? (which I imagine would cause some kind of heart attack or death from shock, or maybe leave them permanently insane, or both.)

You could reflavour PHANTASMAL KILLER to act like that. You wouldn't have to change the mechanics.

Sounds like Power Word: Kill or Finger of Death with extra steps.

This is part of Early Judgment.

Terrible Remorse?

Awaken the Devoured does something like that.