I'm not an achievement whore by any means. Truthfully, I stop playing most games once I complete the main storyline, but for some reason, I really wanted to get that grizzly achievement.
... So I went out in the woods where they usually spawn and waited around. The issue I had was that there would often be 3 or 4 of them and in that case, you're pretty much ****ed. So I kept dying but kept trying. Finally I came up with the plan of shooting them with the pistol a few times (just enough to weaken them) then finishing them off with one or two swings of the blade.
"I don't know how to put this...but I'm kind of a big deal"