Start the level "Rockin' The Docks" from the villain campaign "Power Crazed Penguin" on free play or story, if you choose free play, make sure to take bane as a playable character (sometimes he will be left out on free play).
Destroy the chain-fence on the right with the Demolition suit or the Penguin Bombers. select Bane and just keep pressing "B" as soon as you're in range of your first policemen. when they're all gone.
Use Bane's superstrength to get rid of the trailer that's in your way. Now jump in the truck and drive until you're in front of a citizen that gets beaten up behind some glass.
Hop out and start "B"-ing the policemen that come running down the stairs, they'll keep re-spawning so don't worry you run out of cops. Keep "B"-ing them until you get the achievement.