The Enemy Within Add-on for XCOM: Enemy Unknown has 30 achievements.
Jump two stories in one move in single player
Proc Combat Rush on the entire squad (min. 4)
Field a fully enhanced squad and win the mission
Deal with the newest global threat
Make certain of the new threat's location
Cause an enemy to suicide
Deploy three tactical subsystems on a single soldier in single player
Kill an elite enemy Sniper with one of your own snipers in single player
Complete Furies
Kill a Muton Berserker in melee combat in single player
Kill an elite enemy Medic with explosive damage in single player
Get a Soldier to have 5 modifications in single player
Eliminate an enemy's shield and kill it on the same turn in single player
Complete Deluge
Beat a new special mission without losing any assets
Modify a soldier in single player
Augment a soldier in single player
Eliminate all alien waves
Get at least 4 kills with XCOM Base Security personnel
Eradicate the infestation
Stop a squad member from suffocating in single player
Beat the game without buying a Squad Size upgrade (Classic+ difficulty)
Use Collateral Damage to blow up a car in single player
Field a squad with 4 augmented soldiers, each with a different base ability and win the mission
Field a squad consisting entirely of augmented soldiers and SHIVs (min. 4) and win the mission
Field a squad where all members have at least two modifications (min. 4) and win the mission
Kill an enemy as it is psionically attacking you in single player
Have your special-duty soldier kill three enemies in the same mission
Kill an unseen enemy detected by a specially modified soldier in single player
Designate a highly decorated soldier as the Volunteer