This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Resident Evil: Revelations
Rachael's death in Revelations. Trapped and cornered, as an Ooze kills her she desperately pleads for help, tearfully wishing this was all a bad dream. And then she becomes the very thing she fought against...
Back to Rachael again, one of herMadness Mantras is: Somebody! Please, somebody... HELP ME!
Her diary is rather tragic too: Rachael was fully aware while she mutated, writing down her increasingly bloody changes in gradually more simplified text, until eventually the diary is unreadable from all the blood on it. The last intelligible page has only three words:
"need doctor bad"
The fate of Il Veltro. Sure, they might technically be villains, but imagine being betrayed and trapped underwater with monsters everywhere for a year and being forced to watch the only friends you've got mutate and die around you. It's no wonder Norman went insane.
The Comms Officer, doing his job to send out a Distress Signal, despite nightmarishly mutating into a Scagdead. That's loyalty. Rest easy Sparky, you are releived.
Poor fellow still thinks he's a human too. He can be heard screaming "Stop! I'm human!" when you shoot him.