Glues Your Daddy?G 10

You will need to have completed story mode and purchased Lord Business before you can unlock this. Load up Level 10 - Infiltrate the Octan Tower in Free Play and progress all the way through this level until you're in the last room full of red lasers.

Once you're in this room, select Lord Business as one of your characters and Ma or Pa Cop as your other character. Then as Lord Business shoot both Ma and Pa Cop to unlock the achievement.

Here's a quick video I made showing how I was able to unlock it: