Ryu Kumon's backstory in Ranma 1/2, due mostly to Mood Whiplash: This is a series where no one dies and we don't even see death in the past, but he saw his father accidently kill himself and destroy his house when he was six
The final two episodes of the anime. It sums up Ranma's life, caught between his sense of honour, his curse, and Genma's jerkassery.
What makes the scene powerful, beyond any reasonings or lack thereof behind it, is the absolutely perfect pacing. Akane slaps Ranma and tearfully says she won't try helping him anymore and then turns away from him (as a sad violin tune is heard in the background, if you're watching the anime), Ranma realizes that she means what she said this time and tries to make amends, Ryoga believes he's running away attacks with his bandanna and Ranma kicks it aside before trying to talk to Akane for the second time. Akane then turns while repeating that she's not gonna give him a hand ever again — and SWISH', the haircut comes. Then Akane's cut hair falls to the ground...
Another primarily in-universe tear-jerker is Mousse's dramatic speech in his return story about how he has loved Shampoo all his life and tried over and over to make her accept his feelings, eternally being rejected. The entire audience bursts into tears over this and even Ranma, who Mousse was just trying to kill (and who almost had his fiancee turned into a duck by Mousse), notes that this story makes him feel sorry for Mousse.
At the conclusion of the Shinnosuke arc, Ranma takes the forgetful boy aside to thank him for his help, and for saving Akane's life when she was a little girl. Shinnosuke, of the sieve-like memory, claims to not know what he's talking about and that he's never met any "Akane". But then she immediately comes up to say goodbye, and Shinnosuke's inner thoughts lament that he can't be with her even though he loves her, while Akane's say that she's sorry she can't reciprocate. Meanwhile, Ranma, who is usually every bit as jealous over Akane as she is over him, and who fought Shinnosuke when he thought the latter was stealing her away, recognizes what's going on and silently turns away to let the two of them have their final farewell.
The moment when Ranma sees Akane die near the end of the manga. Ranma freezes right before shutting down, as if he can't comprehend what just happened. And when his life is threatened afterwards, it doesn't seem to matter. He's completely uncaring about whether he'll live or die. Even when Ranma's out of danger, he, unable to cope, does nothing but sit there and stare at her old clothing. It isn't until they take that away, that he reacts violently and breaks down. Even if you hate Akane Tendo's guts, Ranma's reaction to it all is just heartbreaking.
Somewhat later, he sits with her in his arms and tells her what a stupid girl she is for interfering like that. Then he pauses and punches himself in the face, because that's what she'd have done at that point in the conversation. It's... well, tearjerking.