But what is this based on? It seems Flash's powers are always based upon momentum. That's the only explanation for him being able to program computers at lightspeed but still get ambushed by explosions and knifed by something with Captain America-level reflexes.
What do I mean by that? ok, let's say Flash was circling the earth over and over again when the 3-2-1 hit. Then I'd say that Flash takes out Xavier no question. But it seems that when Flash is in a still state, or in the very beginning of a run that his reaction time is comparatively slow. That's how he gets ambushed and attacked by flying Boomerangs and guys with swords in the first place.
Now, I know your answer is going to be, "PIS" - but let's think about this. I think PIS is too readily used to dismiss things people don't like about characters. I don't believe that PIS should be a subjective thing, though that's how it's being used on this board. PIS, to me, should be strictly and ob jectively defined as, "Actions that take place that are contrary to established and consistent aspects of a character's powers, actions or abilities". Superman getting KO'ed by Venom is PIS because he consistently withstands 100s of times more powerful attacks. Flash getting KO'ed by a guy throwing a boomerang is not, because there's actually no majority precedent saying that it shouldn't happen.
You've named a couple of debatable instances where Flash has reacted at FTL speeds. But there are FAR MORE instances where Flash is caught off-guard when he's at a standing or beginning running state. That says to me that Flash has *human* level initial thought time, but as he accelerates, so too do his reflexes and reaction times. If we're going to declare that the hundreds of instances where he's tagged by non FTL characters are PIS, it would have to be outweighed by thousands of instances where he's been unable to be ambushed. That doesn't exist.
So by strict math, in reality, if we're looking at PIS objectively, then if anything, we'd actually have to throw out his FTL *initial* reaction times rahter than his failure to *initially* reacted at FTL speeds. Because, sad as it is to admit, Deathstroke isn't the only time Flash was punked by a non-speedster.
So going by strict definition, at 3-2-1 go, with Flash starting from a stopped state and Xavier a mile away, they should both process the GO at around the same time, and they should both identify the target at the same time. But Xavier can both identify the target AND take action against the target simultaneously because thought and action are identical to a telepath. Flash still has the burden of identifying the target and then actually running to the target and punching the target. Given Flash's *actual* history and the *majority* of his showings, that's not going to happen before Xavier gets out his single thought.
Does that make sense?
I'm headed to the airport and leaving Paris now. I'll write more when I'm in Amsterdam.