Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: The Sound of Music
The children are so depressed after Maria leaves.
Rolf's Face-Heel Turn, poor Liesel just couldn't understand why he was acting so coldly towards her, even when she tries to flirt he coldly tells her "I'm now occupied with more important matters. And your father better be too if he knows what's good for him!"
Captain singing Edelweiss for the last time, he can't finish the song as he is saying goodbye to his beloved country.
It's also a tearjerker on a meta level as this was the last song Rodgers and Hammerstein wrote together before Hammerstein's death.
The Captain's major Defrosting Ice Queen moment when he overhears his children singing "The Sound of Music" and joins in, and then goes to apologize to Maria.