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