Melee from behind = crit/massive damage?

I've noticed with the new hunting knife that any time i manage to hit an enemy in the back it does 100 damage. Is this for all melee weapons or just a sepcial effect of the hunting knife?

 

Weapons have an Armor Penetration number that modifies how much damage the weapon does to monsters. If it has the same armor pen as a monster's level, it does normal damage, but if it has higher armor pen, that damage gets multiplied. You're probably killing monsters with a threat level of 1 or 2, and the armor pen is making it 1-shot things. They're removing this system tho

 

It would be nice if weapons like knifes did extra damage when you hit a monster in the back. I wonder if they are planning on adding that.

 

Oh that explains it. glad they are removing it then