This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Next Avengers: Heroes of Tomorrow
Watching James trying desperately to make some kind of connection to his late father through the machine built in his likeness.
Seeing all those "trophies" in Ultron's fortress was very unsettling. The tattered cowls and broken armor of hundreds of fallen heroes, proudly on display.
Even though she gets rescued at the last second, watching Toruun, who is a teenager at best, suffocate is rough. In the last few moments, she's obviously trying to say some sort of prayer to her father, but all we can hear is her gasping for breath.