Here is the full list of all 46 Trash Squad achievements.
Unlock 3 skins for each of 10 characters.
Kill 10000 monsters.
Unlock 3 skins for each of 5 characters.
Hire 35 mercenaries.
Collect seeds playing as Mud Thing.
Unlock 15 character skins.
Achieve rank 2.
Destroy 1200 elements not including walls.
Unlock 10 character skins.
Unlock 7 character skins.
Unlock 8 characters.
Kill 5000 monsters.
Kill 40 mini bosses.
Collect robot parts playing as Welder.
Complete the game in Cannonade mode.
Kill 50 bosses.
Hire 15 mercenaries.
Kill 25 mini bosses.
Open 50 chests.
Destroy 600 elements not including walls.
Destroy 5000 walls.
Kill 30 bosses.
Unlock 3 skins for a single character.
Complete the game in Nightmare mode.
Kill 25 bosses.
Unlock 3 character skins.
Collect 2000 armour units in total.
Destroy 400 environment elements except for walls.
Open 30 chests.
Unlock 4 characters.
Complete the game in Horde mode.
Destroy 300 elements not including walls.
Kill 10 mini bosses.
Kill 1500 monsters.
Complete the game in Elite mode.
Destroy 2500 walls.
Open 20 chests.
Kill 1000 monsters.
Hire 5 mercenaries.
Complete the game in Normal mode.
Kill 5 bosses.
Destroy 600 walls.
Destroy 500 walls.
Open 5 chests.
Kill a chicken in the Composter.
Unlock 1 character.