That thing is called Azi Dahaka, and it isn't at all necessary. You just have to do the platforms in the right order, and then you will be able to pass the final checkpoint without trouble. You can talk to the machine on the left of the screen to see the order in which the pillars must be activated. Or you can go to gamefaqs.com and check the FFX-2 section for the "Final Dungeon Musical Pillars Diagram." Just be patient and see how the different pillars move. If you mess up, you can talk the machine and reset the pillars and start over.

However, if you just want to beat it, then you just have to get around it's defenses. It has an insanely high defense against both physical and magical attacks. So you must use attacks like gambling, darkness, some of the mascot abilities, or catnip + trigger happy. The above stated strategy works pretty well.