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