Don abandoning Alice, and their later reunion, when she forgives him. Too bad it ends up with him being infected and then killing her. Also, on that same scene, Don trying to fight the infection as it takes over his body. It doesn't help also that you're forced to watch Alice get beaten up by her husband..
Alice's death is just so damn depressing: Abandoned by her husband for dead, becoming a carrier, meaning she could have been vital to creating a cure for the Rage Virus, only to have a Hope Spot with reuniting and forgiving Don... and then getting beaten to death by her husband who she infected. Damn does the universe hate her.
Doyle's death. Not helped that before he was burned to death, he winks to Tammy and Andy, as if trying to assure them that while he'll die, they'll be safe.
The old woman at the start, watching her husband die before being killed herself.
Andy's reaction when he finds out that his father is now infected and is now trying to kill him.
