It's the one boss where you have to keep moving around on the tiles in the Zanarkand Cloister of Trials. I read on gamefaqs that you use provoke on it, but when I do that it just completely rapes Tidus...and then it sweeps the rest of my party. I'm only good at this game AFTER you get most of the monsters unlocked in the arena. (*cough* Don Tonberry!) I find Yunalesca and this dumb boss the hardest two since you are not able to get good gear until after. The only decent armor piece I have is the Magic Counter Buckler for Tidus. Mind you I am under leveled for the most part, Lulu doesn't have any of the level 3 spells, Yuna still doesn't have Curaga, Rikku just learned Bribe and Auron just passed by the Zombie Strike (or whatever) sphere node.
I remember this guy, he has like two sword arm things, and you move around on the coloured lighted platforms. This guy pissed me off a bit as well, my older brother beat him so easy. I don't remember how I bet him though, used Tidus, Auron and Wakka though, with occasionally Yuna coming in.
I should probably recast my vote on this game's difficulty. Easy --> Hard, no medium in between. (kind of like Guitar Hero/Rock Band) I have 3 characters with Steal now (Yuna because she was right next to it on her White Mage sphere path), and still no good items for remodeling. edit: finally beat this guy. did just enough damage to summon ALL of the Aeons saving Bahamut for last. I seriously had to cross my fingers hoping that he would do more than 9999 to kill him. I got 9999+ and overkill. It was either that or have Yuna get hit 3 times and start over.
this boss is just tricky that's all not that hard if you still are stuck watch this my tatics are in the video self explaining but if you still have any questions feel free to reply or ask i will explain the tactic more http://www.youtube.com/watch?v=_-5k-xhCG5I&feature=PlayList&p=F9DFA84C904C3F69