So it occurs to me that a lot of the "Big Bads" of the series are pretty generically evil. You have to look to side antagonists and villains if you want more sympathetic backstories or motivations.

The only real exceptions to this are:

Kuja - Mostly becomes sympathetic later in the game when you better understand what drove him to be evil.

Seymour - Pretty much is the main villain of the game as Sin is a force of nature and Yu Yevon has no mind. Jecht is also not a villain. Seymour had a pretty crappy childhood and his parents were both awful. He joined up with a corrupt church and learned everything they preached was bogus and they intended to keep a cycle of death and misery going forever.

Shuyin - A vengeful ghost who was driven insane by reliving the death of his loved one for a thousand years. Mostly just wants to kill the world to stop being reminded of his tragic last moments.

...and that's about it. At least in my view.

However I've brought this up elsewhere and it seems not everyone shares my view. So this topic is about which of the main villains are tragic. The first three I listed are inarguable as the narrative quite plainly wants you to feel sorry for them,e ven if you don't. These others are a bit trickier:

The Emperor - Something about his daughter and being manipulated by Satan. Only addressed in a book and never even hinted at in the game.

Xande - Terrified of dying but apparently has very little in the way of actual development or whatever. I don't really know a I have not played this game.

Kefka - Kinda sort vaguely because he went insane. This is only said in an optional line somewhere though and is never really properly addressed as far s i know. so I reject him.

Sephiroth - Again, kinda sorta vaguely because he went insane. Depending on if you subsribe to the Jenova Control interpretation, this also makes him a lot more pitiable. However no one ever expresses any remorse for Sephiroth, and indeed he has no real humanity or redeemable features by the time of the game. This is why I disqualify him from the list.

Ultimecia - Again with the kinda sort vaguely quality. She has about two lines that hint at her having something resembling a sad past/motive but it is never developed once in the game. I reject her as a candidate because of this.

Vayne - If you believe his wanton mass murder was justified in freeing humanity from the Occuria. I do not. All the war and death in the game is his fault and he has the stated goal of enslaving all of Ivalice under his rule. In short he's only replacing one tyrant with another, destroying any noble aspects of his actions. Moreover, he was far more ruthless than the gods he so wanted to defeat.

Barthandalus - Fated to never die and to serve humanity forever. Acts like a jerk for the whole game and doesn't come off as very tragic, in spite of the bum deal his god handed him.

So...yeah. Let's rap people. Who belongs in the Sympathetic Villain Group?