Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tearjerker: The NeverEnding Story
The scenes where Bastian discovers the truth about the lion Grograman, and sits with him so he won't be alone.
Artax's death. And he knows he'll die, but he can't find it in his heart to resist. So he tells Atreyu to let go and stop trying to save him so he won't drown too, then gently tells him to look away so he won't have to see him go under. Atreyu does, crying the entire time.
The ending, in which Atreyu and Falkor make up and part with Bastian and set out to tie up the story's loose ends.
"ARTAX!" Every last second of that scene, as Artax sinks to his death, with Atreyu crying and begging him to move. The fade out following is absolutely heartwrenching.
It's an in-universe example as well, since Bastian has to stop reading the book to wipe away his tears at this point.
The "Good, strong hands" sequence.
A meta-example: how the rock biter's character was changed in the third movie, compared with above scene.
In the second movie, the scene showing Bastian's last memory with his dying mother.
The extra heartbreak is that we see this memory because Bastian made a wish. He not only forgets that specific moment, but his mother entirely.