I am stuck in Via Infinito on level 80. I cannot beat the Chac boss......

Your best chance at getting to level 100 in via Infinito.

1. You train long and hard until you get really strong and you still may have trouble, so you know that item "cat nip" you got on level 40 use that. Whenever you die just use Phenix down to make you in the yellow health. Then every attack you do does 9,999 damage. So equip the gunner to that person and use trigger happy. It does about 120,000 if you have trigger happy lvl. 3 mastered.

2. It is still very hard to get to level 100 so some battles(espesially in the 90's) you may have to escape from them. A little advice don't save after you get to level 100 save once you get to level 99 so you can get to the yellow health before facing the bosses. The first boss can be killed with like 2 or 3 of the 9,999 trigger happys, but the second is hard.

Good luck

Use remedy as soon as it stones you. No accessory will prevent being turned to stone.

Look this is what you want to do forget catnip you'll be better off getting chac oversouled so he wont do heavens charachat and when he uses stone gaze he wont be able to break people as easy he'll miss more often or how to do that is go to zanarkand ruins and fight the same fiend as chac untill hes oversouled do not kill him run from battle when you get back to chac he'll be oversouled so no heavens charachat and just get your items together and remedy or soft, mega potions and mega phoenix downs and keep up with the speed watch chac when hes charging he point his body directly at who'll he attack next and you'll get em equip defense gg's so that you can take strong attacks such as valiant luster and items such as crystal gloves

Make sure one of the players has on catnip.. I don't know if this works every time but I used the Pupu platter that Rikku has with her mascot dress sphere. It took all my problems away;)