Here is the full list of all 50 Injustice: Gods Among Us achievements worth 1,000 gamerscore.
Reach Level 100
Beat All S.T.A.R. Lab Missions (Excluding DLC)
Complete All S.T.A.R. Lab Missions with 3 Stars
Get 100 Stars in S.T.A.R. Lab Mode
Complete Classic Battle with all characters
Unlock everything in Archives
Unlock all costumes in the Archives
Play 200 complete Online Matches
Win 100 complete Online Matches
Complete 100% of Story Mode
Win all story mode minigames
Complete 50% of Story Mode
Perform every level interaction once
Cause maximum damage in all Arenas (does not include Practice mode)
Win 10 complete Ranked matches
Win 1 complete Ranked match
Perform every Meter Burn special move of every character
Knock opponent through all transitions across all levels
Perform every special move of every character
Perform every character's supermove
Perform a 10 hit combo with every character
Defeat a Survivor
Dethrone the King in an online match
Win a single online match
Enter Online Practice with someone on your friends list
Complete Classic Battle with any character
Win a Clash sequence with any character
Vote Correctly in a KOTH match
Defeat every Villain With Batman
Reach Level 10
Unlock a costume in the Archives
Make a comeback when at low health (10% or less)
Send an opponent through all three Metropolis transitions in one fight
Win a match as Deathstroke without missing a shot (minimum 12 shots)
Win with Batman using every special move and his Supermove
Win a match with Green Arrow using only arrows
Use every interactable and win in a multiplayer match
Win a multiplayer match with a timeout
Perform 8 throws and win in a multiplayer match
Equip a new Icon
Equip a new Background Image
Enter Practice Mode
Knock an opponent through a transition
Equip a new Character Portrait
View Your Hero Card
Get 3 stars on 1 S.T.A.R. Lab Mission
Complete 1 S.T.A.R. Lab Mission
Win a match with the super move of any character
Complete Tutorial
Complete Battle Mode