With heavier 158-180 gr, even some 200 gr loads out there, a 357 is plenty gun for any deer on the planet as long as you use at least a 4" barrel and 6"+ would be even better. Your only limitation is the range you can hit from. Most of those loads will give complete penetration well beyond 100 yards. They would also be fine for typical sized black bear at reasonable ranges. It is all about bullet construction and shot placement.
When you get into animals larger than deer the larger magnum calibers start to look better