I'm shocked that not many people have included Sito Jaxa from "Lower Decks" in this thread. Hurt more than the one episode Lal.
The end of "The Inner Light" hurts too.
Another scene that's being ignored is from "The Sound of Her Voice," when the Defiant crew bonds with that captain light years away, en route to rescuing her. When they get there, they find that she's actually been dead for a long time, and that their communication with her was possible due to some time-loop. That episode didn't get to you guys?
Oh, "Pinocchio is broken," from "The Measure of a Man."