This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / The Little Mermaid II: Return to the Sea
The entire emotional ordeal (and dismal failure) for Melody at her own 12th birthday party. She's already considered strange by her peers, and her parents' encouragement before the party eases her worries and helps her to believe that everything will be alright. But disaster strikes (through no fault of her own), she's utterly humiliated, everyone laughs at her and she flees the ballroom in tears. Seeing her crying alone in her bedroom afterwards is difficult to watch.
Ariel trying so hard to console Melody, but to no avail.