This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Rumbling Hearts
Rumbling Hearts is a series of connected, sequential tear jerkers. The saddest moment is probably in the 14th and last episode, when Haruka tells Takayuki that they can never be together, even though Takayuki spent years pining for while she was in a coma, practically going insane and nearly ruining his relationship with Mitsuki over her. It was especially bad for this troper because he expected the series to be another light-hearted high school slice-of-life drama. Big mistake.
Anything involving Mitsuki post that one accident could really count since literally everything good in her life goes into a downward spiral. Starting from having to see her best friend spiral to despair, abandoning her swimming career, sacrifices her virginity to keep that friend sane, then hated by her successor because of 'cheating' with her big sister's boyfriend for that, always reminded that I Coulda Been a Contender, said best friend snaps and drives her out when she tells the truth, nearly got into Enjo Kosai with Dull Eyes of Unhappiness, topped with a painful Laughing Mad and even quits her Office Lady job because she thought she's got nothing more and would just falter into obscurity. All of them not easy to watch, but the eventual reconciliation with Takayuki, despite losing everything, and the promise to restart anew from scratch, is also powerful enough to jerk your tears of happiness for at least a Bittersweet Ending for Mitsuki rather than a Downer one.