The time travellers who were flung to the "wrong" point in time and spent years living as temporal fish out of water with nobody to relate to. Particularly so in the case of Kiera's partner, who arrived in 1975. Imagine being sent back to the 1970s from 2013, never mind 2077. The worst part is that she's suffering from severe Alzheimer's, which was cured in her original time.
Kiera dealing with the loss of her son in "Second Opinion".
Kellog's breakdown when Maddie, his supposed grandmother dies in front of him, especially after the reveal that his sister was killed in a similar manner.
Emily dying in Alec Sadler's arms.
In a flashback to 2067, Kiera admits she's joining the military not to protect her family (it was good timing), but because she believes it's the right thing to do. The "crime" she protected them from was owning books.
In the 2070s, you can have debts piled on just for not being sufficiently zealous in saving corporate barons even if it would be dangerous to do so. A mixture of heartwarming and tear-jerker for this in Kiera's case since she saves two children when her boss is more concerned about the financial loss from said wealthy people.
And now one of the Alec Sadlers is a prisoner of the Freelancers, leaving Emily to think he abandoned her.
Sonya has just watched Liber8 effectively cease functioning as a group due to the multiple whammies of learning that at least half its members had secret agendas — most notably, Curtis Chen for the Freelancers — and that their actions at least partly precipitated an even uglier Crapsack World than Kiera's "past" of 2035 with corporate gulag complexes. In short, once more than one person gains the secret of time travel, it is possible for the multiple travellers from multiple timelines to work at cross-purposes in ways which create drastic, unpredictable changes. The "soldiers" in Liber8 are at least able to roll with what has happened, and Lucas is a tech wizard and while time travel seems to hurt his brain, he's cognizant enough of the implications to not waste time grasping at straws. But Sonya's forlorn sense of hope that Liber8 can accomplish what they set out to do is a starkly moving contrast to the rest of the group's utter cynicism.
Travis tries to convince Sonya to move up north with him now that Liber8 is gone, but she still wants to do one more job. She ends up sacrificing herself to kill Dillon, and the scene where Travis finds out doesn't even need words to show how devastated he is.
Kiera accepts that "her" timeline is gone for good, even as she asks the surviving Alec Sadler to build a better future than his other self would have done.