A bear can be a serious threat to a human.
It is possible to kill a bear with a small caliber pistol, but the odds are better if using 38 spec +P and up. Especially with my favorite, 357 mag. (with 158gr JHP at high end of velocity range).
Kodiak Bears? Total other world. 50 caliber is not too large.
Thanks for your interesting posts and some useful advice.
357 mag. is what I carry on my mountain property for just that. Hope I never have to use it. Where I live the black bears are fairly easy to deal with/run away from humans. Normally I yell and shoo them away like I would a raccoon. But running into a mom with cubs would be a different situation entirely!