Seems a bit juvenile making combat some extremely violent thing that could possibly ban all Role Playing Games.
Gamers just like the extreme nature of a Quentin Tarantino Style Combat. Combat as described in D&D is a series of blows and parries until a hit is made.
Is it just fighters that do the dirty tricks?
What about the tricksy thief? Nay ye are not old skew enough! There be no thieves! Well poo to you all! If you make it a subclass of the fighter it's even better! The backstab ability to do double damage is great for the Quentin Tarantino Style Combat forms of violence.
The backstabs can be treated as broken necks, decapitations, and any other form of gory display. When an enemy dies horribly a morale role is needed for the rest of it's group.
The enemy might just run away!