X isn't linear. What the hell are you smoking? Did you even explore for the side quests? I bet you don't even know what the toughest boss in the game is. I'll give you a hint: It takes 50 minutes of constantly doing 99.999+ per person, per turn, and taking upwards 10k damage a hit from this boss, to kill it.
You not only have to find a way to break the 9.999 damage cap, you need to break the HP cap.