Mettle leading people to safety, only to have them all mowed down by machine gun fire. He lances the mech doing it with a lamp pole, but sees he killed the pilot and goes into a little bit of shock. Tigra has to ask him to keep going, even when he's wracked with guilt.
Veil and her quest to rescue a little girl's mother, she succeeds, but the mother is gunned down right in front of the daughter.
Hazmat and Mettle get an excellent moment during when they go to sacrifice themselves to let half the cast escape two of the Worthy. Tearjerker, Heartwarming and Awesome, all crowned.
Hazmat: No. But let's go anyway.
In the Shattered Heroes arc. Adult Finesse is completely incapable of even recognizing her own daughter.
In the second Avengers vs. X-Men Arc, there's Juston's Sentinel.
Sentinel: Unit Will not abandon Juston. Not ever. No matter what. Primary Directive Over-Ride. Protect Juston.
Finesse, gifted with the ability to mimic any fighting skill she sees, thinks the Taskmaster might be her father because of their similar power. They spar to get the readings from one another and Taskmaster tells her that the mimicry power comes at a cost: the loss of long-term memory. They might be related; they might not be. But not only will he eventually forget the entire conversation they had, he won't even remember who she is:
Taskmaster: I wanted ta fight you 'cause... I thought if I remembered your moves, I might remember you. But all your moves are somebody else's. Just like mine.
Hank's broken reaction when he finally has to admit that Jocasta is right that he's not able to bring Jan back whole yet, and that Jan would have hated to come back as anything less after having had to see her own mother live her life as a vegetable after a car accident. Just the look on his face when he finally forces himself to let go of his obsessive quest and say goodbye is crushing. And then later he discovers the body he was trying to revive wasn't even her and she's still nothing but scattered molecules out in the void somewhere.
A lot of moments in the last two issues are Tearjerkers in retrospect, now that Avengers Arena has killed off half the cast. Especially Mettle and Rockslide bonding, and the whole graduation.