Well how easy is it to know what you're doing?
Can it be overloaded with electricty?
Can it be overcome by sheer force?
Don't most people have to be trained in a specific fighting style just to circumvent the shields?
If I may cite the last time a Holtzman shield user was in this competition, the only way we seemed to figure he could be killed was by detonating a bomb at his feet. And people STILL disputed that. Am I the only one who seriously thinks they're overpowered?
No, you're not.
Also, more specifically, the only way we figured the Punisher could kill Idaho was (iirc) by lobbing firebombs at him so that the heat and smoke would force him to drop the shield to breathe (at which point the Punisher could spray the area with gunfire). If Paul has metabolism control, even that won't work on him.
As for electricity and force-
yes, but only in gratuitous quantities- think railguns and nuclear weapons, which our contestants won't possess. The only contestant I can see (at an admittedly cursory examination) that obviously stands a chance against this guy is Static.
Addendum: Sauron, Kikadia, or Armstrong
might be able to break one, depending on exactly how high their super-strength is, but this seems doubtful (They'd be better off trying to restrain him and press a fist through his throat). Youmu's sword techniques allow her to (theoretically) move up to a quarter of the speed of light, which might transfer enough energy to collapse the shield, but it requires a soft target that she can easily slice through when moving that fast-- impact with a Holtzman shield at that speed would probably kill her outright. Her phantom half could also penetrate the shield (being incorporeal, it doesn't interact with the shield at all), but making him feel chilly isn't really an effective weapon (since it couldn't deliver attacks inside the shield, it being skin-tight- and he could even ignore
that with metabolism control).