I personally don't think knives or melee attacks in general should ever instant kill because a pistol or shotgun should be the first thing you use in close quarters combat, not a knife.
If it were up to me, slicing people in arteries would be the only way to get knife instant kills and there would be no commando lunge.
If it were up to me, slicing people in arteries would be the only way to get knife instant kills and there would be no commando lunge.