Can't say it enough...handguns SUCK at stopping people!
And they always will. The movie industry has injured and killed more people with other misconceptions..."One shot, and he flew through the air." UH HUH We carry handguns because they are portable, not because they are powerful.
The attempt to use the one shot stop as a unit of measure is STATISTICAL analysis. Humans are not math problems, that's why they win medals for gallantry, heroism, or ignoring their own extreme peril in combat. Turn that around and use that energy in a felonious way....hmmmmmm.
People do the unexpected most of the time, that includes when you are trying to stop their behavior with a gun.