Ultimecia. I just couldn't stand that she pretty much came out of nowhere. I wouldn't have as much of a problem with her coming out of nowhere if there had been another villian that had been the focus before that, but there wasn't a single villian to focus on for the majority of the three discs leading up to Ultimecia. The focus just jumped all over the place the entire time. Had Edea remained the instrument for Ultimecia right up until about the end of the third disc or so, I think the game would have worked a lot better.