Here is the full list of all 51 Injustice: Gods Among Us trophies - there are 38 bronze, 10 silver, 2 gold and 1 platinum.
You've unlocked all Trophies!
Complete Battle Mode
Reach Level 100
Complete All S.T.A.R. Lab Missions with 3 Stars
Unlock everything in the Archives
Beat All S.T.A.R. Lab Missions (Excluding DLC)
Knock opponent through all transitions across all levels
Complete Classic Battle with all characters
Perform every level interaction once
Perform every Meter Burn special move of every character
Perform every special move of every character
Get 100 Stars in S.T.A.R. Lab Mode
Defeat every Villain With Batman
Unlock All costumes in the Archives
Perform every character's supermove
Perform a 10 hit combo with every character
Complete 100% of Story Mode
Win all story mode minigames
Complete 50% of Story Mode
Complete Classic Battle with any character
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
Make a comeback when at low health (10% or less)
Win with Batman using every special move and his Supermove
Complete Tutorial
Send an opponent through all three Metropolis transitions in one fight
Unlock a costume in the Archives
Play 200 complete Online Matches
Cause maximum damage in all Arenas (does not include Practice mode)
Win 100 complete Online Matches
Reach Level 10
Perform 8 throws and win in a multiplayer match
Defeat a Survivor
Enter Online Practice with someone on your friends list
Dethrone the King in an online match
Win a match as Deathstroke without missing a shot (minimum 12 shots)
Vote Correctly in a KOTH match
Get 3 stars on 1 S.T.A.R. Lab Mission
Complete 1 S.T.A.R. Lab Mission
Win 10 complete Ranked matches
Win a match with the super move of any character
Win a Clash sequence with any character
Equip a new Icon
Equip a new Character Portrait
Equip a new Background Image
View Your Hero Card
Win 1 complete Ranked match
Win a single online match
Knock an opponent through a transition
Enter Practice Mode