Who would win in a fight between a lion and a black bear?

Neither, as they live on different continents and would never meet in nature.
The lion for sure would defeat the black bear with ease. Lions weigh 500 pounds, while black bears weigh 400 pounds, and a lion is quite stronger than a black bear. With sharper claws and thicker paws, the lion would strike the black bear to death. Also, lions have better body resistance.