The proper big stick is anything from .480 Ruger to S&W 500.
If you can control them. Most people can’t shoot those well enough to hit a bear when he’s still far enough away from them. Especially if they have a short bbl.
The biggest hand cannon that most people can shoot is probably the 44 magnum with at least a 6” barrel, for some weight out front and a longer sight radius. And even for that, you need to practice.
Probably better to have a nice 18.5” bbl 12ga pump loaded with slugs. Or maybe alternating slug and 00 buck.