What kind of bear? There are at least three major types in AK.
Personally, for blackies, I was happy carrying a modern controlled-expansion hollowpoint and DoubleTap rounds that I chrono'd and found lived up to the factory claims. (Chrono any round in your gun, of course, before being satisfied that it'll do as is claimed.) Buffalo Bore, DT, Cor-Bon have all made ammo that I've chrono'd as living up to the factory claims - I'm not sure that's always true of all ammo in all individual guns (and I've heard that it's not always true) so be wary.
If you're talking brown/griz or white bear country, I'd want nothing but penetration. I believe that any 10mm 200-grainer traveling 1200 fps will give you adequate penetration. On those behemoths, though, you had better study anatomy and hope to have precise shot-placement and a big dose of luck on your side as well. You might consider choosing a round that you've practiced rapid-fire with, because if you find yourself in a situation where you need a handgun against a griz or polar bear, you'll probably want to shoot it a lot very fast.
