LogFAQs > #967195940

If you are being literal with "the villain" or "the antagonist" in that they have to be characters, then it's Sin. But really this question misses the central conflict of FFX which is against power structures and The Cycle.

Sin physically embodies the cycle so that's the closest. No, it doesn't have much of a personality and is more of a force of nature, but that's not an argument against it being a character. You could apply this to like, Godzilla, you wouldn't say Godzilla isn't a character.

Seymour is doing a similar thing by personifying the Church, Jecht is the source of so many of Tidus's issues, but Sin and the Cycle are bigger than them and ends up literally assimilating these other things.