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