@Popeye:
Well the reason they are beating him in the future, is so they can go back to the past. So to stop him in the ast they have to beat him in the future. Also i was thinking about it, if the there are so many paths, that means even when they go back, half the futures will be the result of him being stopped but the rest are if they fail to stop him in the past. The only way to stop him for sure is stop Irie in the future when he bumps into Byakuran. Simply go back in time, stop Byakuran, wait ten years, be at the moment Irie bumps into Byakuran and grab him so they never meet. That is the only real solution to this problem. But this is just opinion, the mangaka has full control over what makes sense and what doesnt.
Wasn't Irie the one who made everyone come to the future?
And yeah, that's what I meant by stopping Bya's past.. Go back and just kill Irie so he would have never even met Bya thus never allowing him to go to the future.. but then again.. with all these "paths" there could be other iries that travel to the future.. all this dimension travelling and stuff is confusing -_- too much branching out..
it was way easier to grasp in Melancholy of Haruhi since everything was linear-ish