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.
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
Unlock the warehouse exit in Episode 2
Find the Black Order-eliminating electric switch in Episode 2
Complete Episode 2 on any difficulty
Get stepped on by the Giant Golem in Episode 3
Escape the Nari-possessed vending machine room in Episode 3
Look at all "The Great Langtini" posters littering Times Square in Episode 3
Destroy the Giant Golem in Episode 3
Complete Episode 3 on any difficulty
Destroy a Blood Spider Queen in Episode 4
Defeat the first Alpha Werewolf in Episode 4
Eavesdrop on the Black Order as they cage up a Werewolf in Episode 4
Complete Episode 4 on any difficulty
Defeat the Minotaur in Episode 5
Entice the Minotaur to destroy all Graveyard wall sections in Episode 5
Defeat the Griffon in Episode 5
Complete Episode 5 on any difficulty
Run all Council Base lab experiments in Episode 6
Shoot down the low flying Griffons in Episode 6
Complete Episode 6 on any difficulty
Cause the crane to drop the metal beams in Episode 7
Take out the power to the Black Order outpost in Episode 7
Complete Episode 7 on any difficulty
Survive the double Minotaur attack in Episode 8
The Lead Designer apologizes for writing the terrible pun "DouBull TrouBull" - have some points
Free Vivian from captivity in Episode 8
Complete Episode 8 on any difficulty
Complete game on Easy difficulty
Complete game on Normal difficulty
Complete game on Hard difficulty
Collect 1/2 of PDA pick-ups
Collect all PDA pick-ups
Fire all 8 projectile weapons in Single Player at least once
Use Animus to change the frequency of an Aniform Control Device in Single Player
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