This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Young Avengers
The scene at the end of the second arc, in which Hulkling scatters his mother's ashes at the Avenger's Mansion.
Another one in Young Avengers Presents #2, which is also Hulkling-orientated, where his biological father, Captain Marvel, apparently came back to life through a time skip just long enough to meet up with Hulking and find out Hulking is his son and they share a touching moment where Captain Marvel promises if he has time before having to go back to his own time just before he dies he'll spend it with Hulkling but the sad part comes when on a rather beautiful panel and a page before it, where Captain Marvel flies off and they share a rather touching moment.
Hulking's thought bubble: For just a second, I could pretend I had a Dad. I could pretend I'm not alone in the world. For just a second.
Captain Marvel: I will see you again... If I get the chance...Before I return to my own time.
Hulking: That would be nice. (Thought bubble) And it would have been nice... But I never saw him alive again.
Civil War. Five Words. "I want him to die."
Children's Crusade #8 gives us Cassie's death. Issue 9 follows up with Iron Lad killing Vision II in cold blood, and the rest of the team opting not to restore him from one of his back-ups, as that would mean they'd have to tell him that Cassie was dead.
Children's Crusade #9 opened with Scott Lang cradling his daughter's dead body. As he cries, he states that he was the one who was supposed to die, not Cassie.
Iron Lad was trying to prevent himself from being Kang the Conqueror, but seems to have failed. The worst part is that he doesn't even seem to realise that he can't fight what he's going to become, and that trying to prevent it is only making it happen.
Admit it. We all wanted to hug Woobie!Wiccan during Children's Crusade #9.
Speed: This is a war we're fighting.And yes people get hurt. People die. But you don't stop fighting or the bad guys win.
Wiccan: I don't know who the bad guys are anymore. The Avengers thought it was Wanda. I thought it was the Avengers. Eli thought it was Doom. But it turned out to be me. I'm the bad guy...
The talk Teddy has with Tommy at the end of Children's Crusade #9. Tommy is often treated as an outsider and we hardly get to know him as a person outside of his Speed persona - so seeing Teddy taking such an interest in him is lovely, but heart-breaking. Tommy just doesn't know anywhere to go with his life except for being a Young Avenger and now he's told he's the only one left.
Later, when Billy talks to his parents and tries to explain the situation and say goodbye, even through he knows they won't understand what's going on.
Also, dialogues between Loki and Ghost!Kid Loki can jump from incredibly funny to heartwrenching on the line-to-line basis.
As Miss America fights one of her mothers, she's seen screaming that she only wanted the best for America and everyone.
Red Mom: We only wanted what was best for you, America! We only wanted what was best for everyone.
Miss America: I know! [punches her mother] I know. [punches again] Me too.
Issue #12 is one moment after another.
Kate and Noh-Varr have a quiet moment on his ship where they admit they're scared.
America has tears in her eyes as she wishes Billy good luck in her own way: "Just don't fuck up."
Issue #13 has Loki confessing to all his crimes, including manipulating the team and killing Kid Loki and his following Heroic BSOD in which he begs America to kill him. There is also Kate and Noh-Varr's bitter breakup and Loki abandons the gang, commenting "He's gone".
Issue #14: America's backstory. Little America was a cute princess until her guardians tell her that their world is stabilized and she realizes that her mothers are dead. She decides to run away from home.
Issue #7: Teddy's conversation with Noh-Varr, where he reveals just how much Loki's suggestion that Billy accidentally forced Teddy to love him — or created him in the first place — has been eating away at Teddy. You can tell that it's killing him inside.
Teddy: (thinking) I see Billy shatter. I try to work out how I could change into something to protect me, or him. There's got to be some form I can take that doesn't hurt anyone. My power is useless here. I just tell him everything. He asks me to stay the night. I say no. I may change my mind. And with a wisdom, fear and strength I didn't expect...