Here is the full list of all 83 Slime 3K: Rise Against Despot achievements.
Get a level 3 copy of "Heretic's Fork"
Kill 999 Black Swordsmen
Unlock every achievement!
Kill 100000 Newbies
Kill 6000 Specters
Get a level 3 copy of Triangle of Darkness
Unlock every ability
Kill 3000 Brains
Unlock all Slime starting setups
Get a level 3 copy of Tiny Spring
Get a level 3 copy of Coin Launcher
Kill 10 Thornies
Get a level 3 copy of Super Scytherang
Get a level 3 copy of Disco
Get a level 3 copy of Meteorite Satellites
Kill 30000 Tomatoes
Get a level 3 copy of Candy Bomb
Get a level 3 copy of Olive Gun
Get a level 3 copy of Obedient Doc
Get a level 3 copy of Caliperang
Kill 300 Bots
Kill 10000 Bees
Kill 2000 Martial Arts Masters
Beat level 10
Kill 5000 Doc Ocs
Kill 666 Maniacs
Kill 3000 Ballerinas
Kill 300 Mantraps
Get a level 3 copy of Nuggets of Darkness
Get a level 3 copy of Fire Beam
Get a level 3 copy of Bananarang
Get a level 3 copy of Supreme Gun
Get a level 3 copy of Homing Loogie
Get a level 3 copy of Money Box
Get a level 3 copy of Flashes
Kill 200 Shieldbearers
Beat level 9
Get a level 3 copy of Needle Shotgun
Get a level 3 copy of Watermelon Launcher
Get a level 3 copy of Blaster
Beat level 8
Beat level 7
Beat level 6
Get a level 3 copy of Random Nails
Get a level 3 copy of Dark Side
Beat level 5
Get a level 3 copy of Supreme Shotgun
Beat level 4
Kill 1000 Stilt-Walkers
Get a level 3 copy of Fiery Horizon
Kill 300 Pain Lovers
Get a level 3 copy of Rocket Launcher
Get a level 3 copy of Shotgun
Beat level 3
Kill 600 Laser Swordsmen
Kill 666 Fire Mages
Kill 50 Fridge Men
Get a level 3 copy of Scytherang
Get a level 3 copy of Assault Rifle
Kill 1 Wheelman
Beat level 2
Kill 2 Watchers
Get a level 3 copy of Pistol
Get a level 3 copy of Obedient Zombie
Kill 10 Madmen
Beat level 1