At true "combat distances" (within 5-10 feet) damn near any caliber will put your assailant down. It might not kill him, but it'll stop him long enough for the average armed citizen to get out of harm's way.
I sure wish you would tell that to the drugged up assailants around here. Many take on several hits and still injure or kill their victims. One guy nicknamed "Cuz" took three direct, rapid hits to the chest from a .357 mag at somewhere around 10 feet. He continued on to fatally stab the victim three times and then attack her husband before finally running out of the store. Happens often just with different calibers and people.
Sure, some people are stopped with one or two shots. As I have mentioned before, some die of their wounds when the wound was not fatal. But a drugged up idiot does not always feel the pain or understand he has been shot. I have seen several committ their bad deed and drive their self to the hospital. Once, back in the late 60's, I was standing next to a guy that was hit in the shoulder. He never knew it until he went inside and we noticed blood coming from his shoulder. Within minutes, he was in pain.