This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Stupid Mario Brothers
Link's death in Act 2 of the movie counts, especially since he was one of the more lovable characters the show had.
When Ash is able to catch every Pokémon (at the time) before Gary Oak does, Gary responds by throwing a tantrum at being defeated. Surprisingly, some may actually find it heartbreaking to watch as he collapses into tears, though obviously most will find it to be a light dose of karma and a comedic moment.
There's also Mario's heartfelt goodbye at the end of the series finale. Just the way he says it with such a sincere amount of gratitude, this scene struck home with many fans, especially ones who followed the series since it's first season.