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