Tear Jerker / Star Control

• The whole story of the Androsynth. They are enslaved by the rest of the human race, then, after they escape, they are enslaved again by the Ur-Quan Kzer-Za. Then, they are wiped out by the Orz. (perhaps. It can actually be worse.) The Arilou, who seem to have gone to such great lengths to protect humanity from the Orz, do not seem to have felt any need to warn the Androsynth, who, after all, were just the other half of the human race, about the dangers of their inter-dimensional fatigue experiments. Their whole history seems to be one undeserved catastrophe after another.
• The Melnorme, the descendants of the Mael-Num telling the story of the Kzer-Za's namesake, and asking the Captain to try to understand the motivations of their collectively traumatized former allies who had tried to kill/enslave them all.
  Captain, if these positions seem to you... extreme, or unwarranted, you must remember that the Ur-Quan had been unwilling slaves for millenia, and that each of them had to remain in agony for years in order to defeat the Dnyarri. The followers of Kzer-Za and Kohr-Ah were all on the brink of madness, but neither side would submit [...]
• To a similar extent, the Yehat and the Shofixti. Imagine the situation from Yehat eyes: you find an alien race in your exploration of space, and liking its culture decide to uplift said race to have their members considered as your children fighting alongside you, having carried to space their culture. When your allies have been defeated, both of you mount a large fleet to defend the Shofixti star system, just to find your Queen has ordered a general retreat and have to leave them on their own. As you leave, you watch the battle and how your children attempt to stop the Ur-Quan onslaught in vain just to watch their star detonating, killing both a sizable part of the invading fleet only to give the Kohr-Ah a numerical advantage over the Kzer-Za allowing the former to finally defeat the latter and seemingly all the Shofixti, and having to live onwards with both the shame of that act and the one of being Battle Thralls when, as the Ur-Quan arrive to your homeworld and you're prepared to fight to the death, the Queen allies with them.
• When you tell Tanaka or Katana about the Alliance having been defeated despite his people's sacrifice, he lets out a shrill, soul-wrenching scream:
  Tanaka/Katana: HYAIEEE! GYAIEEE! AIEEE! I am a defeated warrior! A worthless shell! I must die!
• The history of the Ur-Quan Kzer-za and Kohr-Ah. Originally, they were part of a group called The Sentient Milieu. Then one day a scout came across a group of aliens called the Dnyarri. The Dnyarri took control of the Ur-Quan and used them to destroy the other races. Until they found a way to free themselves, the next several millennia were the mental equivalent of being locked in a closet and raped constantly. The only way to free themselves from the Dnyarri's control was to put themselves in a state of constant agony. For an untold number of years. And even worse, due to Genetic Memory, the scars of the past are just as fresh now as when they were first rent.
• The circumstances of the creation of the Taalo Shield. The Taalo themselves were immune to psychic influence; the shield they were working on in their final days wasn't for them, but for their Ur-Quan friends, to free them from the Dnyarri. But the Ur-Quan never found it.
• Talking to the Slylandro gives a glimpse of how friendly the Milieu-era Ur-Quan could be with a species that, like the Taalo, they could really socialize with in a way they couldn't even with one another. The Dnyarri had a lot to answer for.
  Content to Hover: But the Ur-Quan were such good guys! They had lots of interesting things to tell us about and they never got impatient with our questions.