Warning: Spoilers Off applies to this page. Proceed at your own risk.
Dissidia manages to give KEFKA a Tear Jerker. They re-do a speech of his way back from FFVI. Then he goes on a rant about destruction being the only reason worth living, and he blows up.
Kefka: Why create when it will only be destroyed? Why cling to life, knowing you have to die? None of it will have meant anything once you do. Terra: We fight to protect what we hold dear. As long as you have that, you can find the meaning on your own. Kefka: Meaning, schmeaning. The whole world's going bye-bye, you included! Life, dreams, hope... Where do they come from, and where do they go? None of that JUNK is enough to fulfill your hearts! DESTRUCTION! DESTRUCTION IS WHAT MAKES LIFE WORTH LIVING! Destroy... destroy... destroy... LET'S DESTROY EVERYTHING! *He explodes and fades away, with a sobbing laugh*
And after he's gone, Terra reflects on Kefka's motivations.
Terra: It was your broken heart. You were trying to fill it with destruction.
Just reading the speech might make it look like a diabolical villain's demoralization speech, but when you actually HEAR it...he actually sounds sad. You know, until the whole "destruction" part. And even then, when he vanishes, it's followed by his final laugh; you can hear his voice breaking, it's as much a sob as a laugh.
Truth in Television. That's how nihilism, which was essentially Kefka's driving force, usually works.
Ultimecia, ironically when you don't beat her with Squall in Shade Impulse. They're just a few words on a white screen, but reading it makes you realize something about her...
"Can you still remember the days when you were a child? The sensations, the words, the feelings... Time...it will not wait. No matter how hard you hold on, it escapes you. And...I..."
She wasn't always a megalomaniacal tyrant. She wants Time Compression not simply out of revenge, but because she misses the time she can't go back to. The time before she got her sorceress powers. The last time she was really happy. It turns her from a Giant Space Flea from Nowhere into a very relatable Woobie, Destroyer of Worlds. All in four, un-voiced sentences. Bravo, Square. (However, one must note this is the speech she gives when she is on the brink of defeat in her original game, so it was always there, Dissidia just clarified on it more.)
Lightning: Bring it on! I don't need a second chance!
In episode 000 of Dissidia 012, once ghosts of the fallen warriors appear. Some characters, like Lightning, show disdain towards the Great Will, while others are simply caught in despair at their predicament. Their lines strike hard, especially as compared to the characters' story arcs in Dissidia and their own games.
Terra: I can't do this anymore... I wish I were still just a puppet. I wish I never found out anything...''
Yuna: ...It was just false hope, made up by us warriors... Our story had been written from the start.''
Kuja's entire backstory. He's initially bored with the cycle and plans to betray Chaos, and tries to help Zidane and his friends take him down; he's even on good terms with Zidane. Then Kefka gets wind of his plot, and for no other reason than to make Kuja miserable (Kefka cares more about random destruction than Chaos's plans), not only does Kefka ruin his scheme, he makes him look like he was going to betray Zidane and the others all along.
What sells it is Kuja's utter resignation to it when it happens. There's no attempt to defend himself or change anyone's mind, he simply slips back into his role as a villain as simply as though putting on an old glove. Plus the implications that he intentionally took to offensive against Zidane and his allies to give them a chance to get away, all without them ever knowing that he was truly trying to help them.
Cosmos sacrificing herself to save the Warrior of Light near the end of 012. You can hear the fear in his anguished call to her.
Chaos killing Cosmos, it was just so fast... and brutal.
Not to mention Tidus and Firion during the whole thing.
Hell, everyone's reaction.
It's even Harsher in Hindsight. When you read all the reports and put the backstory together, you realize, in a way, Chaos killed his own mother.
Despite the fact that he still doesnt exhibit much emotion, we don't even get to see his initial reaction to Cosmos death. What the Warrior of Light says as he and the others begin to fade away speaks volumes.
Warrior of Light: There is not even a speck of light. I am in absolute darkness.
If you listen closely the tone of his voice is no longer confident yet focused like usual, he sounds wistful and almost heartbroken.
In Duodeciem, you learn how Jecht became a Warrior of Chaos. It's also how Tidus became a Warrior of Cosmos. As Yuna's helping Tidus remember them properly, the Emperor shows up to kill off Yuna with a Flare. Tidus protects her and would have simply died. While Yuna and Mateus have at it, Jecht saves his son the only way he can, transferring his powers of Harmony to Tidus. Tidus would reawaken in the thirteenth cycle, and Jecht was an empty shell, giving the Emperor a new plan.
Duodecim also sheds light on how Firion came to dream of a world covered in wild roses. Laguna once found a rose while travelling with Squall and Firion. When Firion asks what kind of flower it is, Laguna pulls an answer out of his ass and calls it a "wild rose". Squall doesn't buy it, but the name stirs something in Firion, bringing about a vague memory (in Final Fantasy II, he was a part of the "Wild Rose Rebellion"), and he decides to keep it with him. Later, he misplaces the rose. Lightning finds it and hangs onto it until Firion asks for it back, then she asks Firion to let her have it again once his memories return, since she believes it could help her regain her memories as well. It was a touching moment, but alas, Lightning would perish before Firion could oblige her...
Considering how good Dissdia is at fleshing out the personalities of past characters, it should come as no surprise that even someone like Garland is shown in a sympathetic light.
In Dissdia 012, Tidus is dying and asks his father one last request: "Take care of Yuna."
Hell, the entire tragedy of Cid of the Lufaine and his family. The man tries to help end a war only to get strong-armed and backstabbed by the very people he'd been trying to help, while his (surrogate) son is forced to hurt people against his will. Then, in a final blow Cid sees his wife apparently shot dead before he, his son, and his wife's clone are sucked up into another dimension.
When encountering Exdeath after Cosmos's death, after he explains the true nature of the crystals to the heroes. If the Warrior of Light happens to be in the party, he lowers his head and mournfully asks "Cosmos...why?"