They show him build it in another video.

That’s nice.

How does that change the fact it’s used, and functions, like oversized brass knuckles?

Can we just enjoy the video of a man hitting things with a thing?

In fallout, it's pretty easy to punch someone in the crotch with a powerfist so hard that they die from a fatal groin explosion. While being punched by this powerfist in the balls would likely hurt, I don't think I'd be exploding anytime soon.

Power not-ergonomic-sledge-hammer.
Power shoulder-destroyer.
That was a hollow core door, so you could probably do that with a pair of steel toe boots.

But I'm being an asshole, that looks fun. Five apologies for my cynicism.

The powerfist in the game has some kind of pneumatic action that launches a weight forwards when you strike. Thus it adds "power" to your "fist."

This is just a big weight on his hand. No power. They should have just called it "fist."

You can see the pneumatic action in another video. Still... he should give us a demonstration with a proper door. Or a crotch.

Ya canna' change the laws of physics, Raggamuffin. Action vs Reaction.

Adding a hydraulic that moves the weight forward will push against your arm, reducing the effect of your muscles. All this thing can do is add to the inertia of your arm by adding mass (and LEDs -- woo!).

And that's not a hollow core door. It looks like a (very thin) steel door with a styrofoam center.

I'd say that is very high carbon steel then, about 99%. And invisible styrofoam. You're right about the pneumatics pushing back against the arm, slowing it, but wrong about the effect that would have on the punch. The weight would be accelerated to whatever speed by the guy's arm, then the pneumatics would push against both the guy's arm and the weight. Whatever force that guy's arm can put up to the pneumatics, even if it's dead weight, will be the force put on the weight, accelerating it further. Thus, Power Fist/exploded arm bones.

Power sack full of power doorknobs

^^^

You're thinking of Iron Man, not Power Fist.

come on Bort that was clearly a Fallout reference