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