The entire Dumbledore's Armyverse is rife with them. This author is a sadist. Good, but a sadist. You'll be rereading JKR's Snape backstory and Harry's final walk into the forest just to cheer yourself up after this author forces you to take a long, hard look at what it means when teenagers go to war.
Terry Boot tried to use the Killing Curse on Michael Corner because he didn't want his best friend to suffer anymore.
The outtake Standing Witness, which is from Terry's point of view during and after the above-mentioned Killing Curse episode.
The entire Battle of Hogwarts, but especially the chapter after that, where Ernie sacrifices his life for his wife and unborn child, in a way that is beautiful and sob-worthy.
Seamus' speech in the second. And then Colin's in the eighth.
The aftermath of the final battle, particularly Romilda's family not recognizing her and Pansy crying over her sister.