While I don't recommend fighting large predators with a knife, to answer your question:

The best Busse kin knife for the task, be it bear or montain lion or feral dog or pig, is the 8" Pure Bred Fighter, (or, for a smaller knife, the 6" version).



It is the most efficient at penetration of any Busse kin knife, and a heck of a slasher, too. It also is probably the fastest and most controlled in hand. It also has one of the most secure grips.

By the way, it is not correct to say that grizzlies and and black bears do not atack people as prey. It is comparatively rare, but it does happen. It is most commonly when the bear is either young and still experimenting and learning what to eat, or when it is starving and willing to take a chance on anything, or when it is old and feeble and sees a human as an easy target.

If a bear is attacking you out of perceived self defense (usually when the bear has been startled) or defense of cubs, then playing dead, until you are no longer perceived as a threat, can be sound. If a bear attacks you predaceously, then fighting back is necessary.

A good book to read, if you want to learn more about the subject, is Bear Attacks: Their Causes and Avoidance, by Stephen Herrero.