OP, if you accept that a 510 grain 458 Win mag into the foot will not be sufficient for a bear or a deer, and if you accept that a .22 Long Rifle behind the ear has taken both bear and deer in Canada, you have a pretty much LARGE selection for suitable arms and cartridges. Is pretty much all about you and your abilities, not the gear.
An older trapper fellow up here is totally proud and impressed with his .243 Win Ruger Compact - he takes multiple deer, bear, wolves, and moose with it every year. Not a hope of convincing him that there is a better rifle or cartridge available.
On the other hand, we have had 3 different black bears in the neighbourhood over past few days - two blacks and a cinnamon phase - my wife and dog had the smaller black one cross the road, while the "ladies" were taking their morning walk, in front of them within about 50 feet, and within 50 feet of our house, this morning. So beside me at my desk, I have a Mauser 9.3x62 and a sleeve of shells. So gotta pick the fights that you really want to get into, and when you are an old guy like me, tend to also want to win. Our 7 year old, 65 pound female Bulldog does not appear to think like that - very protective of my wife - so bear, strange dog or whatever is going to get charged - does not seem to consider possibility of "losing" a scrap - so Grandpa will need a good rifle, ready to bail her butt out of the situation that she likely created...