Despite Dr. Glasner being such an awful guy, the story of how Abigail died before his eyes is a tragedy.
Hue's dog, one of the few beings who kept him company after he talked Shade into letting him keep him. Dog naturally grew old and died sometime, and to have someone to talk to, Hue kept his body in stasis.
EBE1's background story. He witnessed his entire species and his planet dying when one of their suns collapsed.
Hue's despair at the end of chapter 17, when Rose is to be taken away from him for good, and all her memories of him get deleted. He's even done protesting because he's so utterly crushed, just cries in silence as he shuffles away to his room.
Young Longus finding out that his first love Brevis has died in war. He wants to say his farewell and ends up curled up and crying on Brevis' corpse — which is when Brevis' brother Magnus comes in, completely losing it and starting to shout homophobic slurs at Longus for "bringing shame" on the memory of Brevis.
Fatima telling her story in chapter 21: she'd been stranded on earth, trying to contact her people who wouldn't answer, hence she assumed that none of them had survived the war. And the last thing she had seen before her escape capsule launched was her partner being attacked by Reptoids.
Rose finding out that her mother was very happy to leave the humans and didn't particularly miss her family on earth, not caring at all about Rose's father and not enough about Rose herself that she ever even visited her.