The Onslaught Add-on for Call of Duty: Ghosts (Xbox 360) has 11 achievements worth 250 gamerscore.
Gain access to the Compound area in Nightfall in Regular or Hardcore difficulty.
Gain access to the Facility in Nightfall in Regular or Hardcore difficulty.
Kill the Breeder for the first time in Nightfall in Regular or Hardcore difficulty.
Kill the Breeder in less than 5 minutes in Nightfall in Regular or Hardcore difficulty.
Kill 50 Cryptids with the Venom-X weapon in Nightfall in Regular or Hardcore difficulty.
Complete all challenges and kill the Breeder in Nightfall in Regular or Hardcore difficulty.
Kill the Breeder while using a Relic in Nightfall in Regular or Hardcore difficulty.
Kill 5 Phantoms in one game in Nightfall in Regular or Hardcore difficulty.
Kill a Rhino with only a pistol in Nightfall in Regular or Hardcore difficulty.
Find all the intel hidden in Nightfall.
Complete the Egg-Stra XP challenge and then destroy a hive in the Onslaught DLC package.