Here is the full list of all 21 The Bug Butcher trophies - there are 21 bronze.
Kill 1000 enemies with the chain lightning gun in any single game mode
Kill 1000 enemies with the laser beam in any single game mode
Kill 1000 enemies with the rocket launcher in any single game mode
Beat the target Combo for all levels on floor 05!
Kill 1000 enemies with the gatling gun in any single game mode
Collect 3 stars on every level of floor 5!
Collect 3 stars on every level of floor 4!
Beat the target Combo for all levels on floor 04!
Beat the target Combo for all levels on floor 02!
Collect 3 stars on every level of floor 2!
Unlock all powerups in arcade mode
Don't use any powerup in level 18
Unlock all weapons in arcade mode
Unlock all perks in arcade mode
Dash into a frozen face hugger enemy on the ground
Survive 30 seconds without shooting on level 9 in HARD
Don't let the spider touch a scientist on level 10
Don't use any powerup in level 6
Don't use any powerup in level 12
Complete 5 rounds without dying
Kill 1000 enemies with machine gun in any single game mode