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