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Tear Jerker: Future Diary
Admit it, by this point you would have wanted them to win.
Tsubaki's backstory is both this and horrific. As well as the captured Yuno's screams of "No! My first time will be with Yuki!" as Tsubaki orders her followers to gang-rape her to lure Yukiteru out and as revenge for all the pain she went through.
Akise's death, if you liked that character. If not, it was one of the better CMOA's.
And just before that, all of Yuki's friends dying. The exact circumstances behind it make the whole thing so much worse.
Minene's death. Poor girl has to see Nishijima die in front of her eyes first, then does a Heroic Sacrifice for Yukki...only for it not to do anything whatsoever. And for worse, she would've led a peaceful life with Nishijima, if not for his death.
Minene: Ah...That's right... I wanted to be saved, too...!
Subverted when it's revealed she's still alive.
Yuno's breakdown in Chapter 56. At the end of it, she's begging for Yuki to hate her.
When Minene holds the school hostage, Yuki, who believes he is about to die, makes a confession to Yuno about how even though he pretended to indifferent to everything; he actually wanted friends. At the end of his confession, he calls himself a loser and breaks down crying.
It gets worse. Yuno tries to cheer Yuki up by telling him everything will be better once they get to the other students - after all, they're his friends! Except then they immediately turn him over to Minene to be killed. Yuki isn't even shocked by the betrayal for long, reasoning that there was no reason for anyone to be friends with a pathetic person like him, and just hopes that his death will make him useful somehow.
2nd-world Yuki'sfate after he becomes God? The guy spends ten-thousand years floating in the void that has become the 2nd-world, staring at his diary endlessly as it remains frozen on the exact date and time of the last message it recorded and shows: "Yuno died.", blaming himself endlessly for it. Mur Mur, the only other person to have survived from that world, even asks Yuki when he will try out his powers. Not use. Try out. He's literally done nothing since he became God but blame himself for being unable to stop Yuno's suicide for 10 000 years. Thankfully, the Gainax Ending that follows not too long afterwards results in the HAPPY END.
The flashback where Yuki and Wakaba go shopping and Yuno runs interference is pretty funny. The previous flashback scene where Yuno is not chosen because "her parents are very strict with her curfew" and she has a flashback to being locked in her cage while begging her abusive mother to let her go out and the one at the end where Yuno recalls her parents's abuse and deaths and the one where Yukki mourns his dead mother obsessively in the present... not so much.
What makes the bunny suit one even worse is if you remember that according to another flashback, this is the Yuno from the 2nd-world, and that the 1st-world's Yuno appears and murders her shortly after that flashback ended.