ive said this 1000 times on different one piece places buit Pound was literally introduced being stabbed in the head and ignoring it. Randolph is set up as one of Big Mom's better homies that arent napoleon, zeus, and pandora, and he straight plants his spear in the back of Pound's head the first time Pound shows up, then Pound reacts with more surprise at seeing the straw hats again than he does taking a hit to the dome
if Oven had cut his back, or heart, or torso, he'd be dead, but zoro could probably hit pound in the back of the head with an onigiri and hed be fine