(I have never fired any of these or other magnum semi-automatic pistols. My opinions are based upon shooting the 357 and 44 magnum calibers in revolvers, and then as little as I could possibly get away with.)

.357 magnum semi-auto. Probably manageable. I have problems with that caliber because of a wrist broken in a motorcycle accident in college, but in a pinch this could be shot.

.44 magnum semi-autos. That is a serious cartridge, for a long time considered the upper limit of what could be managed in a handgun.

.50 (50 caliber) semi-auto. The Israelis developed this. Frankly, it's a worthless piece of iron. No one could hold it on target without a serious muzzle break. Someone could fire it once fairly well. However, in my humble opinion, forever after that they'd flinch. And the recoil from the first round would tear the piece out of your hand. After it broke your wrist. And elbow. One serious weapon, but I think an opponent would be more dangerous with a lesser caliber weapon.