VFX and you
His powers have to do with movie effects, like slow motion and zoom. Since some of them, by their nature, affect everyone, I'm making this post as a compromise between being descriptive and dictating other characters reactions. So, the powers in question and their effects are:
Slow: Everything slows down - that is to say, your perceptions slows, and you can react quickly but everyone moves at the same relative speed. But everything is more powerful and dramatic - punches are harder, explosions are more explosive, and everything else that happens when movies are in slow motion
Zoom: This one is tricky for text, but basically comes down to JOE IS THE CENTER OF ATTENTION. It basically means he's about to use a special attack or do something awesome. Focus is inexorably drawn to him, and since we can't have speed-lines, everything around him dims and he lights up. It has been known to paralyze weak-willed enemies simply to have them stand near him while zoomed. They have exploded from sheer awesome when he dodges then zooms in to strike a pose - this is not exaggerating, this is a game mechanic.
Mach Speed: This is the only one that does grant Joe an advantage over everyone else, but for the sake of completion, I'll point out that he does actually look like he's fast-forwarded. Not just running or attacking quickly, but like he was filmed running quickly and someone played it back twice as fast.
Feel free to have your characters react to the slow-down, or the intimidation and attention-grabbing however you like.
[no I didn't delay my reply just to make this icon shut up]

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