Yamamoto attempting to commit suicide after beliving that he will never be able to play baseball again.
Varia Arc
Gokudera's Varia fight for the Storm Ring. The end where Gokudera sacrifices the ring he's been beaten near-death for, because he wants to survive another day for his friends, "I wanted to see the fireworks again, so I came back..."
Tsuna begging for Gokudera to drop out of the ring match despite his resilience to continue fighting.
Tsuna: Stop joking around! Why do you think we're fighting!?! Because we're still gonna have a snowball fight and watch fireworks together! That's why we're fighting! That's why we got stronger!! So that everyone can laugh together again!! If you die, then all that no longer has any meaning, right!?!
When Squalo appears in the Sky Battle and begins talking about Xanxus' past all the while trying to tell him he understands what he feels like... every single time they read/watch it.
Then there is the Cloud fight in the Ring battles. Kyoya beats Gola Mosca easily with one hit despite the creature getting up again. But then we find out the truth: Xanxus put his own adoptive father in Gola Mosca as his POWER SOURCE. When Tsuna shot down Gola Mosca when it got back up, he effectively attacked the ninth boss and nearly killed him. The ninth boss who is described as a nice old man, who looks like a nice old man, who IS a nice old man. Tsuna just attacked him. And the fact that this shocks Tsuna out of Hyper Mode, causing him to blame himself until the dying old man tells him that it isn't, that it's his own weakness that caused all this and after telling them what really happened to Xanxus during the Cradle Affair, he then tells Tsuna about how Reborn tells him all about Tsuna's life and the girl he likes and everything. He admits that Tsuna's a child who isn't suited for being a mafia boss with his soft heart but that's EXACTLY why Tsuna was chosen. At this point he has touched Tsuna's forehead. This is when the real Tearjerking occurs.
Future Arc
When Tsuna arrives in the Future in his own coffin and those pained faces Gokudera makes.
The fight with Gamma. Gokudera's line after Gamma reveals that the Tenth Vongola Boss was gunned down in plain view of many of his subordinates reveals how affected he is by the news of Tsuna's death. Made even worse by the fact that when he loses, Gamma tortures him for information and Gokudera responds by spitting in his face.
"How dare you...HOW DARE YOU BASTARDS! UNFORGIVABLE!"
It's very small, but in the [final cross] theme, the few seconds with Lal. She's by herself in an alleyway, visibly upset, but then she's shadowed, and looks up, shocked, and we see Adult Colonello, standing in front of a careless blue sky, offering her a hand. Then she remembers he's dead and the image of him is wiped away and her eyes go half-lidded again and full of tears. Those six seconds speak volumes about what Colonello means to her.
Spanner's Mini Mosca defending his master, even though he has no combat abilities. It sacrifices itself to give Tsuna time to rescue Spanner, something that clearly pains Spanner. As Tsuna puts it:
"He was just protecting his cherished creator."
While absolutely horrifying, the Deathstalk Squad is this. They are in the manga scientists who mutated and experimented on themselves to make Iris happy, or are abominations made for the sole purpose of being Iris's minions after she manipulated some scientists (and then had the Squad kill them). Iris is abusive to them, pushing them well past their limits.
When everyone visits their homes in the future, Haru (who is having the hardest time with everything) does not feel as if her home or her life then really belongs to her. She starts crying after reading a letter from her parents that feels distant.
Inheritance Ceremony Arc
Anyone who's lost someone they truly loved would understand how Daemon felt when his lover Elena was killed.
Curse of the Rainbow Arc
Yuni with tears in her eyes in Chapter 377: "My heart would be in great pain as if it's being gouged out."
In Chapter 388 Tsuna acts quite upset when he learns that Reborn will either die or become a Vindice member.
