Here is the full list of all 31 Kill Strain trophies - there are 14 bronze, 10 silver, 6 gold and 1 platinum.
Unlock All trophies
Collect 20 unique Augments
Reach lifetime score of 666,666 points
Upgrade 3 Masteries to Max Tier
Complete 10 Missions
Kill 50 Mutants with a MEC
Open an Augment pack
Deal 100,000 damage to a Mercenary base
Turn 20 Mercenaries
Deal 100,000 damage to Mutant base
Complete 30 matches of Kill Strain
Complete matches starting as 5 different characters (Mercenaries or Mutant)
Kill 100 Alpha Strain Pods by throwing an ARCC or with a MEC
Get turned and then turn an ex Mercenary teammate in a match
Kill a total of 80 Mercenaries and 40 Mutants
Spread Strain 250 times
Get at least 3 Gold medals in a match
Survive a Mutant drag by struggling
Save a teammate Mercenary from turning
Get 8 kills without dying in a match
Equip a Mastery to a Mercenary and Mutant
Upgrade a Mastery to Max Tier
Kill 10 Mercenaries
Activate 20 MECs
Be the last Mercenary on your team by the end of a match
Escape death by turning into a MEC with less than 5% health
Kill 10 Mutants
Complete a game as a Mercenary and starting Mutant
Turn your first Mercenary as a starting Mutant
Take 10,000 player damage as a Mutant in one life
Deliver an ARCC at the Drop Zone and kill an Alpha Strain Pod in one match