This is the absolute quickest/ easiest method for those who've beaten the game, or at least to this point. Load up Chapter 11: Trapped
difficulty. This chapter throws you immediately into the action as soon as you're down the stairs, and the starting room alone offers enough enemies to complete this trophy easily, even with a mistake or two early on. Restarts won't set you back any time at all.
difficulty, even the basic starter pistol will allow you critically wound enemies with a single hip-fire (fire without aiming down gun sights) shot, and kill them by following up with a single punch (
). You can do this on other chapters or difficulties, but stronger enemies means more damage required before punching, and therefore more chance for error.
When you spawn, run down the staircase and jump down on its right side where the railing is broken off. You will land next to a Dragon Sniper
. Pick it up, and hug the wall. Use it or normal pistol fire to kill the big, shotgun enemy coming around the corner next to you. Then use your sniper to look at the balcony to the top right, and snipe that guy. Then focus your sniper on the turret fire, directly in front and above you. Peek out from your wall where you picked up the sniper, zoom in, and shoot him in the leg. The sniper will kill him in one shot regardless.
With those three nuisances cleared, simply run around the room, using cover as needed, and hip-fire one pistol round, followed by a punch to kill. So long as you see blood from enemies after you fire, it means your shot hit, and a single melee attack (kick, punch, or slam) should kill them. The game is slightly forgiving towards accidental extra shots/punches during your spree, but not by much. Continue this pattern until it pops.