The Citadel Add-on for Mass Effect 3 has 9 achievements worth 250 gamerscore.
Discover a plot against you.
Go undercover to follow a lead.
Infiltrate an enemy stronghold with your crew.
Stop an out-of-control scheme before it's too late.
Throw a party for your friends.
Win a prize at one of the arcade games.
Investigate a strange occurrence in the combat simulator.
Score 9999 points in the combat simulator on Normal, Hardcore, or Insanity.
Defeat a group of Spectre-level opponents on Normal, Hardcore, or Insanity.