I don't think thats even the issue.. Unless he has some ridiculous durability or can change his form, accelerating to that speed would kill him. Immediately. Not to mention a punch at that speed would completely turn his hands to dust: Wire needs special gloves to make sure he doesn't mangle [i]his[/i] hands when he punches at full power, and that wouldn't even be close to the sound barrier. He does have a normal human body though that wasn't really affected by the awakening though, so theres that.

Either way, its impossible for any PC is likely to be able to take down Polaris at the moment. At all: it took most of the League founders, undeniably the most powerful character's in the League, to take him down before, and you guys are just walking up and punching him. If death was a thing at the moment, then their chances are slim! RP your weakness just as much as your strengths guys! Don't make MrD have to write them in for you when Polaris fights back!