Max Enkaria's death. He barely appeared at the beginning of Rise 1, and he died by being forgotten by everyone.
Haken Losing the use of his legs. Mostly heartbreaking when you know dancing was probably the only thing he was good at.
Laras's death, with Abraham blaming himself for this. Ivanna and Krystal threatening to kill him for that weren't helping.
Fred passing away in Rise 3. After spending two RPs as a walking punching bag and skirting so close to death in the middle of battle, he finally died peacefully in a hospital bed surrounded by family.
The Empire's mind controlling half of Axel's Gang was just a fountain of Tear Jerker moments.
Special mention must be made of Abraham's suicide.
Clyde accidentaly killing the only one for who he truly cared.
Gyver dying in front of Bonnie, who just told him she was pregnant.
The death of Axel's Red Panda, Terrance.
Anything related to Abraham and his wife. Anything.
A truly sad moment, when she dies and the Keyes twins are left to themselves, with their thought-to-be-dead grandfather is looking after them.
Aerion probably outliving all of his friends ...
Haruka dying before even reaching 40, and it is unknown if she ever found Yvonne after she disappeared after the Battle of Homeworld.
To the Hellknights, the death of Heimdall on Factory. Earl lost his shit. And afterward, the reactions of every Hellknights, which most of them can't accept. Especially Zazi and Slice who runs out yelling and crying, and losing an old battle-brother, respectively. He gotbetter.