It looks like we have a lot of ideas about the "smallest" gun we'd trust.
I posted way back when that it would be a 380, which is generally considered a pipsqueek round. But I think it'd do the trick if it ever needed to, as long as I did my part, that is.
I read a lot about stopping power, but I don't think much of it is honest. I'm convinced that handguns in general don't have much stopping power. Rifles and shotguns do. But handguns require good shot placement in order to stop a determined assailant. We've all heard about cases where an individual has absorbed multiple hits from major caliber handguns and not only survived, but suffered little long term damage.
We've also all heard about single shot stops, using the same calibers.
The difference? Where the bullets passed through the targets.
Ya gotta hit 'em where it hurts. All else is minor details.