This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Oz: The Great and Powerful
After seeing his magic act, a Wheelchair Woobie asks Oz if he can make her walk again. Being simple country folk, even her parents beg him to use his magic. Frank admonishes him for not admitting the truth later - that it's all just a trick.
China Girl's introduction, in which her village is destroyed by Evanora and her legs are broken off. Her bitter weeping when she is revealed with her broken legs and tells what happened to her family is especially distressing; even Oz can only look at her silently before he finally thinks of a solution. What makes it even more moving is that it's a Call Back to the prologue in Kansas, where we see Oscar failing to help a girl in a wheelchair who asked him to help her walk again. That girl was played by Joey King, the same actress who voiced the China Girl - and Oscar couldn't afford to let her down again.
Theodora's moment of realization - too late - right after biting that apple may qualify.
Oh, it and what follows qualifies... First comes the pain, then the madness, and then there's nothing left but the hate. It's tragic, powerful stuff.
Theodora reassuring her sister that all she wants is peace. This becomes HEARTBREAKING later on when she has become fully wicked and talks of drenching the yellow brick road in the blood of Oz' citizens, or laughing at what she thinks are those people being mauled by her flying baboons.
Oscar and Glinda are far from unaffected by Theodora's transformation. Oscar seems genuinely horrified once he gets over the shock, while Glinda is just sad because she'd hoped Theodora would see through her sisters lies.
When Oscar fakes his death, and it makes Finley and China Girl weep.