"I doubt there is any land animal short of a rhinoceros/elephant that could fight off a grizzly. Well, or a human with a hunting rifle. "
you forgot the tiger, brown bears always run from tiger; and you forgot hippo too. For the rest Polar bear, Russian bear, Kodiak bear, African lion ar also too much. Seriously I have doubts if a grizzly could even take on a Cape Buffalo or Gaur. Grizzly bears are very over-rated.
For this fight I'll go with the bear, better protected, more aggresive, faster and more weaponary