Smell Something Burning
Kill the crapping gangster with a fireaxe

On the level 'Clean Hit' after you've killed everyone, you should be able to see this guy in the bathroom next to the room with 4 mobsters in it.

To get this achivement, you want to pick up the fire axe in this


and then simply cut his head off!

sometimes some of these achievements wont unlock right away, what I did was play a few (1-3) levels, and it unlocked after i've beaten, or started a new level.