All handgun rounds are underpowered compared to 12 gauge and 30-06.

That said, .22 lr *can* be effective. 380 acpt *can* be effective.

Go ahead and read the details of the Israeli sky marshal who killed several AK-47 wielding terrorists with his Beretta .22 lr pistol with only a 10 shot magazine.

Now, I'd much rather have my .357 magnum or .357 SIG on me. But I live in the real world, and I can't always have a service sized pistol on me. Frankly, those 'experts' who deride anyone who carries a caliber less than a '4', speak from a position of special privilege. These tend to be folks who have jobs and lifestyles that allow them to always carry a large pistol due to relaxed dress standards or general lifestyle. Not all of us works or lives in such a 'gun friendly' enviroment, and sometimes the only option we have a super compact .380 or even smaller.

Carry what you are proficient with, and carry what you can, when you can.