In my opinion the M9-bayonet and Cold steel are actually OP, Due to the game still being beta with some lagg here and there, I can easily 1-hit knife people in either the head or neck/chest and due to there being no player collision (except with your own team sometimes) you can walk through the enemy confusing him and 1-hit stab him/her. Also you have a 2m long stab action and you can stab someone when you start stabbing at 4m distance.
The same lagg also makes knifing a bit UP because lagg from both your enemy and yourself can take the ammount of stabs needed for a kill up to 4