The Harley Quinn's Revenge Add-on for Batman: Arkham City (Xbox 360) has 10 achievements worth 250 gamerscore.
No crimefighter should be without this
Find a way into the secret base
Clean up the Dry Docks
The joke's on who?
Zip Kick 5 different thugs
Shield Bash 5 different thugs
Snap Flash an unarmed thug, an armed thug, an environmental object and a Titan
Defuse all bombs in 3 minutes or less
Use 5 different Quickfire gadgets in one fight as Robin in Harley Quinn's Revenge
Destroy all Harley Balloons