The first time I played this, like a billion years ago that went over my head. He has one of the better character arcs of the series; so much that they'll like two entirely different people. Could you imagine how the Tidus at the start of the game would've reacted if told (SPOILER)he was going to disappear?

Even statistically speaking it shows if you use him the entire game. I had him and Auron in the front line for the entire game and while Auron outdamaged him by alot early on. Near the end of their trees, Auron was still doing more damage in a single hit, but Tidus was going a lot, loooot more than him and was potentially doing more damage. And his HP, for a while he's lagging behind Lulu and Yuna for max HP. But by the end of the game, he's still behind the tanky Auron and Wakka, but has more then the mages and thief. He's like a Magikarp in human form.