What is the best way to kill the bear with your knife to get the Master Hunter Rank in this game! I just can't do it! Anyone got any tips?
The general strategy is to weaken the bear with a few rounds from one of your firearms, and then dodge its attacks and swipe at it with the knife.
The number of bullets depends on what weapon you're using and where you hit them. There's a guide on this page that I found mildly useful, but mostly it just takes practice.
You can also do this on horseback - it's a bit tricky to line up your attacks this way, but if you've got a strong horse that can take a few hits, it can help your survivability a bit. I suggest having a horse at the ready at any rate, just in case the bear decides to flee. It doesn't happen often with bears, but it does happen occasionally.
They also suggest using the lasso, which can cause the bear to temporarily go into an animation that leaves it somewhat vulnerable. I didn't find this to be particularly useful, myself.
If you're at this rank, you've already done the cougars, and they're by far the worst. Keep at it, and you'll eventually knife a bear to death.