Here is the full list of all 21 Dark achievements worth 1,000 gamerscore. It takes around 8-10 hours to unlock all of the achievements on Xbox 360.
Feed on an enemy.
Complete the tutorial.
Meet Blooming in the museum catacombs.
Visit the Geoforge Parks.
Completed the club area in the Atlantis.
Reach the destroyed Sanctuary in the destroyed apartment complex.
Talk to Samantha in the Bunker and learn more about your past.
Chase Samantha in the Bunker level at the end of the game.
Complete the game by defeating Ascension with Rose.
Rescue Tom in the Bunker level before the UV light kills him.
Use Shadow Leap 50 times
Kill 50 enemies who were neither suspicious nor hostile.
Subdue and then Feed on 5 enemies.
Earn ten experience rewards for completing areas without raising the alarm.
Take out or Feed on 50 enemies.
Use Vampiric Powers 50 times.
Distribute 10 Power points amongst the powers as desired.
Distribute 20 Power points amongst the powers as desired.
Find and use 7 PDAs during play
Complete a level without tripping a single alarm.
Learn all the powers and their upgrades.