Full list of all 44 BlackSite: Area 51 achievements worth 1,000 gamerscore. It takes around 20-25 hours to unlock all of the achievements on Xbox 360.
You got more than 400 kills with each weapon
You got more than 200 kills with each weapon
You got more than 100 kills with each weapon
You got more than 10 kills with the Plasma Rifle's detonating projectile in Campaign
You got the squad to help you get more than 250 Focus Fire Kills
You got more than 10 kills using the Antitank Launcher's target-lock in Campaign
You completed all episodes on Red (hard) difficulty
You completed all episodes on Orange (medium) difficulty
You completed Episode 6: Wrecked
You completed all episodes on Yellow (easy) difficulty
You collected all Dossiers
You completed Episode 5: Topside
You brought down a Spore Tower
You brought down a Fire Brute
You killed more than 250 Reborn
You completed Episode 4: Counter Insurgency
You killed more than 25 Drudge using only melee
You completed Episode 3: Rachel
You collected 25 Dossiers
You won more than 50 ranked matches!
You won more than 25 ranked matches
You captured more than 50 flags
You captured more than 25 flags
You won a round of every Xbox LIVE Ranked Match game type
You completed a round of every Xbox LIVE Ranked Match game type
You completed a ranked match of Abduction
You completed a ranked match of Capture The Flag
You captured your first flag
You hosted an Xbox LIVE game of Blacksite (any game type)
You completed a ranked match of Team Deathmatch
You finished first in a ranked match containing a Blacksite Virus Carrier
You won your first ranked match
You completed a ranked match of Deathmatch
You got over 20 kills without dying in a single Versus match!
You played in a game with a Blacksite Virus Carrier
You competed in your first Xbox LIVE game of Blacksite
You got the squad to High Morale more than 20 times
You got 10 kills while the M4 was equipped in Campaign
You completed Episode 2: Quarantine
You got 5 kills with the Scatter Gun’s bouncing projectiles in Campaign
You got more than 10 head shot kills with the pistol in Campaign
You completed Episode 1: Iraq
You got 5 kills while the Sniper Rifle was equipped in Campaign
You collected a Dossier