LogFAQs > #967174524

Seymour also tried to merge with sin and actively destroy everything, that could very easily have been the final boss instead of braska's final aeon and I think is probably more important for the setting's health, seymour controlling sin is probably worse than just letting sin's cycle continue as is. So I'm going to say seymour.

It's hard for me to say yu yevon is the villain despite him creating the cycle, because the reason he did that was to defeat a nation he was at war with.