In Resident Evil: Operation Raccoon City for the PS3 and Xbox 360, you can perform a Close Quarters Combat (CQC) kill that will instantly kill an enemy.
To perform a Close Quarters Combat kill, you first need to melee the enemy until they stagger. Once you see them stagger, immediately press A on the Xbox 360 or X on the PS3 to perform a generic kill, or you can press Y on the Xbox 360 or Triangle on the PS3 to perform a specific kill for the character you’re using.
Note that you can’t perform Close Quarters Combat kills on any heroes or bosses.