Sometimes in my game, i can get a critical attack, does more damage than a normal one, its somewhat random though,
I can shoot them in the face one time and get normal, and then do it again and get a critical attack, you know its a critical when it does that hollow knock sound when it hits them, but I've only found it works with a bow, haven't properly done it with swords yet.
And incase someone thinks I'm mistaking for a sneak attack, this is while we can both see each other, and attacking.
But its not just the face that has given me critical damage, I've shot them in the chest too and its happened, Its weird, anyone else does that??
thought I'd add that to help you out, Hope it does