Here is the full list of all 50 Quantum Theory achievements worth 1,000 gamerscore.
Destroy 50 Watchers. (50/50)
Destroy 20 Watchers. (20/50)
Kill all enemies in Trachea without dying.
Kill the Raven on Hard in 2 minutes or less.
Kill 10 enemies with every firearm Syd can equip. (Melee kills don't count.)
Defeat Diablosis Soma (Thanatos III) on Hard in 3 minutes 30 seconds or less.
Defeat Chaos (Thanatos II) on Hard in 1 minute 30 seconds or less.
Defeat Thanatos on Hard in 1 minute 30 seconds or less.
Kill the Chariot during Thorax on Hard in 1 minute 30 seconds or less.
Kill the Gargantua on Hard in 2 minutes 30 seconds or less.
Kill the Dreadnought on Hard in 2 minutes or less.
Clear The Seed of Gnosis.
Clear the entire game on Hard.
Clear the entire story using only the Revenant.
Land 200 combo throws.
Land 100 full combo attacks. (3 consecutive hits)
Filena killed 50 enemies.
Hit 5 enemies with one shot from the Ifrit.
Shoot down 10 projectiles from the Raven.
Clear Cavitas Cranii.
Clear The Root of the Tower on Hard.
Clear Trachea on Hard.
Clear Lumenosynthetic Reactor 2 on Hard.
Clear The Womb on Hard.
Clear Cavitas Cranii on Hard.
Kill 1000 enemies.
Kill 200 enemies with headshots.
Don't let any teammates who were setting charges go down during the final battle in The Womb.
Obtain the rank of Immortal.
Obtain the rank of Storm.
Obtain the rank of Berserker.
Revive 10 teammates in one match.
Obtain the rank of Slayer.
Kill all other players in an 8-player Deathmatch.
Kill all members of the opposing team alone. (8-player Team Battle)
Obtain the rank of Elite.
Obtain the rank of Commando.
Obtain the rank of Mercenary.
Obtain the rank of Soldier.
Obtain the rank of Novice.
Kill 20 opponents in one match.
Kill 10 opponents in a row during one match.
Clear The Womb.
Kill 100 enemies with melee attacks using the Bloodcleaver.
Clear Lumenosynthetic Reactor 2.
Kill 500 enemies.
Shoot an enemy with a Plasma Lancer from 50m.
Clear Trachea.
Clear The Root of the Tower.
Destroy 1 Watcher. (1/50)