Tear Jerker / Survivor Dogs

• Mickey finally giving up on his human family in Book 3, hoping that if they ever come back they'll know he waited as long as he could. Even Lucky, who hates humans, starts to change his mind about them when he realizes just how much Mickey loved his family.
• Fiery's death, where he gets poisoned by longpaws (dog term for humans) and slowly gets weaker and weaker until he could no longer hold his own in a fight, leading to his death at Terror's jaws. The worst part is that there's nothing that the dogs who had come for him could do.
• Martha gets killed by Blade's dogs. Storm is beyond upset at seeing her foster mother being killed, so much that she challenges Blade to a one-on-one duel.
• After Arrow and Bella's litter of puppies is born in The Exile's Journey, it's revealed that the firstborn puppy (a female named Tufty) was stillborn. Arrow's hello/goodbye speech for her really drives in how much he and Bella grieve for their daughter.
  Arrow: When...when we left the Wild Pack, we had a vision of a new way. A Pack where it doesn't matter what kind of dog you were born. Nip and Scramble will grow up in that pack - but you won't have the chance, Tufty. It hurts. But this Pack won't always be easy. There will be problems, and dangers, and some other dogs will distrust your litter-brothers, even though they've never hurt anyone, just because of who their Father-Dog is. And I'm...glad that you won't have to know what that's like. I wish you had stayed. I wish that you'll know how loved you were. Your Mother-Dog and I are sorry we'll never see you grow. We - we know you would have been a good dog.
• Lucky didn't always distrust people, either humans or other dogs. Bad experiences with an abusive, alcoholic owner as a puppy made him the jaded Lone Dog he is at the start of the series.
• The Leashed Dogs start out as just wanting their owners back. They're clueless about being on their own and don't want to leave their homes until it becomes obvious that they'll die if they stay. It takes a long time for each of them to realize they'll likely never see them again. To make it worse, they don't know why their owners left them alone and see it as abandonment.
• There's a point in the first book where Lucky and Sweet come across a human crushed in rubble. The human has a moment where they smile at the sight of the dogs right before dying.
• The dogs come across a bunch of dead longpaws at one point. One includes a human boy around the same age as Mickey's owner. Though the other dogs consider it abnormal for Mickey to be attached to his former owners, it's still sad seeing his reaction. He gets Lick and Lucky to help him bury the boy's body.