I've recently gotten into The Flash and so been reading about his powers.

What I don't understand is why his typical rouges pose a threat. It seems like there should be very little limit to his powers.

He can go back in time, so if he loses a battle or the bad guys do something, he can go back and preempt it.

In the new 52, he can all but predict the immediate future, so he can see bad things that are going to happen and stop them.

He can phase matter through matter, or let matter pass through him. This means he is all but immune to weapons fire.

I haven't read enough of the old comics so I don't know challenges he had. For a guy who can't be attacked, can time-travel and can race around the globe several times in a minute, I can't imagine there is much that could pose a threat.