The final boss is a story battle. Jeez.

Yunalesca and all of Seymour's forms required a bit of strategy; and annoying cutscenes you keep having to watch over and over. But once you nail down a concrete strategies, they aren't so tough. But I died more than once on little miss Yunalesca the first time.

Of course, by Jecht I already had many things to create 'Trio of 9,999', so nothing was very tough then...but most people seem to forget that the Aeons and Yu Yevon are in fact a story battle and call them easy.