Full list of all 50 Legendary achievements worth 1,000 gamerscore. It takes around 60-80 hours to unlock all of the achievements on Xbox 360.
Completed game on Easy difficulty
Completed Episode 8
Freed Vivian from captivity in Episode 8
The Lead Designer apologizes for writing the terrible pun "DouBull TrouBull" - have some points
Survived the double Minotaur attack in Episode 8
Completed Episode 7
Took out the power to the Black Order outpost in Episode 7
Caused the crane to drop the metal beams in Episode 7
Completed Episode 6
Shot down the low flying Griffons in Episode 6
Fired all 8 projectile weapons in Single Player at least once
Collected 1/2 of PDA pick-ups
Changed the frequency of an Aniform Control Device in Single Player
Completed Episode 5
Defeated the Griffon in Episode 5
Defeated the Minotaur in Episode 5
Caused Minotaur to destroy all Graveyard wall sections in Episode 5
Completed Episode 4
Defeated the first Alpha Werewolf in Episode 4
Destroyed a Blood Spider Queen in Episode 4
Completed Episode 3
Destroyed the Giant Golem in Episode 3
Escaped the Nari-possessed vending machine room in Episode 3
Was stepped on by the Giant Golem in Episode 3
Completed Episode 2
Found the Black Order-eliminating electric switch in Episode 2
Unlocked the warehouse exit in Episode 2
Killed 25 enemies with the Fire Axe in Single Player
Used the Animus Pulse ability 10 times
Completed Episode 1
Created a ramp with the soda machine using your pistol in Episode 1
Chopped your way out of the Internet Café with the Fire Axe in Episode 1
Extinguished the doorway fire using the water valve in Episode 1
Bypassed the electronic lock in Episode 1
Look at all "The Great Langtini" posters littering Times Square in Episode 3
Eavesdrop on the Black Order as they cage up a Werewolf in Episode 4
Run all Council Base lab experiments in Episode 6
Complete game on Normal difficulty
Complete game on Hard difficulty
Collect all PDA pick-ups
Start and finish a ranked Multiplayer match
Fire every weapon available in any ranked Multiplayer match
Fill 50% of your team's Monster Machine with Animus in a ranked 4v4 Multiplayer match
Kill 10 Werewolves in a ranked Multiplayer match without being killed
Kill 10 enemy players in a ranked Multiplayer match without being killed
Ranked 4x4, max Animus match: fill 25% of machine, kill 10 players, 10 werewolves, win the match
Be first place in kills in 10 ranked Multiplayer matches in a row
Survive a ranked 4v4 Multiplayer game without being killed
Play 200 ranked Multiplayer matches
Win 50 ranked Multiplayer matches