You brought the comic book nerd out of me (you brought this on yourself lol), but technically, the flash can superpass Superman or really another superhuman/hero, so long as he’s remotely close to the Speed Force (the thing from which he gets his abilities/powers). The thing with that is, he’s usually never really in the realm of the Speed Force, mainly in most comics with him in it, up until you get to the issue that debuts the Speed Force.
Really if Quik Silver or even Zoom is around him, they easily kick his ass. Not to mention Superman can actually tap into the Speed frequency that the Flash operates in. Not for sustained periods of time though, but enough to put the hurt on him. The movie does a good job of showing what he does for like a few seconds, but in general, Kryptonians thrive on radiation, which I guess you can translate that to increased metabolism concerning how quickly you can move, but in general Superman probably couldn’t sustain that on Krypton while the Flash can pretty much still be quicker than an Attosecond on different planets (Krypton would probably be different since the gravitational pull is like 9x stronger than earth), but then again, Flash has the power of the Speed Force and that thing is almost equivalent to the Phoenix Force (really strong energy basically).
So it’s kind of split into advantages concerning their surroundings. Yea Superman is pretty much an all around badass, but the Flash can pretty much move almost as fast as light itself, and when he’s managed to harness the Speed Force, he can just about tap into time manipulation, which superman isn’t really immune to. The movie doesn’t go into all that for sale of time I guess. But then again, I’m weirdly interested in comic books, and no one gives a hoot about comic books anyways.
Okay I’m done now lol


