13 Mar 2011 13 Mar 2011
To get this achievement easily once you have completed the story
Just start a freeplay on the first level and pick Two-Face, kill a few goons and it should unlock.
Although it says 'in a level', it doesn't have to be the same level. Chances are you killed 10 police officers with him in the storyline.
If you do happen to kill 10 goons and it doesn't pop. Just play 4 - 1 and kill some cops.