You know what? I think I'm not going to DNR anymore, since now I'm getting confused as to what my criteria are >_>
Seymour Guado - 7.0 - Relatively decent, although to be honest, I completely forgot he existed at the end >_> He's big to start, then dies...then comes back with evil Yuna marrying (though, that would be something he suffers from - god, that voice), then dies...then comes back...then dies...then disappears for a bit, then finally shows back up. In between all of this, his backstory is decent - his mother becoming an Aeon setting him on the course to become the thing he hated is relatively neat, and he is bloody persistent, though I can only give so many points for that since...well, I didn't feel like he was that threatening. Still...could go up?
Sin - DNR - Ok, I lied. I...have a lot of trouble ranking Sin, as I feel that the "villainy" of Sin is more in the atmosphere around it, i.e., people like Mika, Seymour, Jecht, etc. I just can't rank him reasonably without think of other issues, and a force of nature alone...feels hard for me to rank on villainy/badness.
Yu Yevon - 5.0 - Really needed a lot more exposure, although it is really neat the entire story around him. Still...not all of that is entirely him, and...it's kind of hard to have feelings for a metroid unless you're Samus Aran >_>
Mika - 6.5 - Eh...while he is excellent for keeping the ritual of suicide going for as long as he did, it is partly everyone in combination too. I also feel like he doesn't have the personality to really push himself to the forefront of my mind, for all that he is a behind-the-scenes guy. Granted, the being unsent and scaring the hell out of the other Maesters and basically sending himself is pretty damn ballsy - "Hah, the world is fucked, kthnxbai Yuna". The deception, though, is a function of everyone in on it, not just him.
Kinoc - 2.5 - As Crystalgate said, helps Auron with his backstory more than himself, and is otherwise just there.
Yunalesca - 4.5 - She's...not that present until later, which kind of sucks. She felt like she was mostly there - I think the game needed to explain a bit more the triangle here of Mika - Yunalesca - Yu Yevon. Her, "this is the best we can do" speech was done already by loads of better people. Granted, a point for fighting the party's "stupidity", unlike Mika (although Mika's is, as the Elf put it, far more haunting).
Jecht - 8.5 - Like I said for Sin, multiple people weave the tapestry of the beast here. Jecht leads it to me - he's not necessarily a villain, but definitely a bad guy to Tardus. Again, I want to make note that I wish the game explained the Fayth/Zanarkand thing a bit better, but I digress. He's good at being the villain he needs to be, and I think he understands that, so it's a good guy in the position of being the bad guy. Neat.
Plot question for FFX - am I remembering this right? Tardus, Jecht, and Zanarkand of the past are dreams of the Fayth, which are the spirits of the dead. Due to Sin's ravages (brought on by Yu Yevon creating the beast as a shell to protect his dream world, a.k.a., Zanarkand before the war with Bevelle), the Fayth, restless and tormented because of this madness, try to stop this - they take their dreams and make them "real" and give them "life" and a "purpose" (Jecht pulled from his dream world into the "real" world, becomes a better person - Tardus, knowing his father is Sin, has a resolve to stop him to come to terms with hating him - thus, Tardus will help push Yuna to defeat Sin the right way, by killing the source, Yu Yevon). In between this, we have the Yevon church that knows all about this (Yu Yevon founding it, and teaching machina are bad after Zanarkand was nuked, punishing the world with Sin's arrival) and keeps everyone in the dark about this (granted, only the higher-ups really know much, I'd assume), Auron (the guardian of Braska, who knows everything, and because he's the equivalent of a Fayth, is able to help them on their quest by bringing Tardus out of the dream into the "real" world, and guide him to the end), and a host of other people with varying knowledge of the situation. I really do like FFX a lot, and the story is rich - the problem is it could use better presentation. FFXII, while with a more general story (that borrows elements from it), does explain things better. Aaaaaaanyway...
Vayne Carudas Solidor - 9.5 - He is neat. Begins as what seems to be a generally good guy! Then you hear a lot about him, and you start to wonder. Then he starts to do some things that are odd as hell. Then he acts like a bad man and kills his daddy. He also LOOKS like the evil politician guy/manipulator/Machiavelli, which is NICE. And he's doing all this to set his brother up as ruler (with the caveat that it's on HIS terms - not the way the senate wants it), and to beat some godlike creatures that, while they can't directly intervene, have shaped history for a long time. He's interesting, though the end is a little odd (again, he's...not really much of a final boss personality), but definitely explainable (Larsa fighting him was the final "test", giving him the strength to lead the way he needs to). The guy's pretty brilliant overall.
Judge Magister Gabranth - 7.0 - Snowfire is right that he falls apart towards the end at Pharos/Bahamut, but that's...supposed to be the point. He begins very set and for the empire, but starts to doubt, and finally feel the connection of brotherhood and honour, and sees that his brother has a point. We do get the conflict - he just doesn't do it in the most...ideal way.
Judge Magister Ghis - 2.0 - Generic and dies really freaking fast. He's present for, what, 3 scenes and a battle? Pathetic.
Doctor Cidolfus Demen Bunansa - 8.0 - Worked with Vayne, the only difference being he's much less present. Nonetheless, still awesome.
Vossler York Azelas - 6.0 - Kind of...off. Similar to Gabranth, except that, well...he does place duty high, but duty to country first. He's very honest in this, and does believe in doing what's right. His betrayal...it was odd, I will agree, but...not so odd to the point it feels completely off, though yeah, points down.
Venat - 5.0 - See Cid and Vayne, subtract more for less time. Also, the parallels I could draw between the Occuria and the Fayth >_>
The Dark King - 1.0 - Come on - even I really can't hype him >_>