Here is the full list of all 78 Slime 3K: Rise Against Despot achievements worth 1,000 gamerscore.
Kill 100000 Newbies
Kill 2 Watchers
Kill 3000 Ballerinas
Kill 10000 Bees
Kill 10 Thornies
Kill 666 Fire Mages
Kill 666 Maniacs
Kill 2000 Martial Arts Masters
Kill 600 Laser Swordsmen
Kill 50 Fridge Men
Kill 999 Black Swordsmen
Kill 300 Bots
Kill 5000 Doc Ocs
Kill 10 Madmen
Kill 3000 Brains
Kill 300 Mantraps
Kill 6000 Specters
Kill 1000 Stilt-Walkers
Kill 200 Shieldbearers
Kill 30000 Tomatoes
Kill 1 Wheelman
Kill 300 Pain Lovers
Beat level 1
Beat level 2
Beat level 3
Beat level 4
Beat level 5
Beat level 6
Beat level 7
Beat level 8
Beat level 9
Beat level 10
Unlock all Slime starting setups
Unlock every ability
Unlock every achievement!
Get a level 3 copy of "Flashes"
Get a level 3 copy of "Pistol"
Get a level 3 copy of "Rocket Launcher"
Get a level 3 copy of "Watermelon Launcher"
Get a level 3 copy of "Scytherang"
Get a level 3 copy of "Super Scytherang"
Get a level 3 copy of "Money Box"
Get a level 3 copy of "Obedient Zombie"
Get a level 3 copy of "Obedient Doc"
Get a level 3 copy of "Fiery Horizon"
Get a level 3 copy of "Nuggets of Darkness"
Get a level 3 copy of "Triangle of Darkness"
Get a level 3 copy of "Supreme Shotgun"
Get a level 3 copy of "Coin Launcher"
Get a level 3 copy of "Caliperang"
Get a level 3 copy of "Bananarang"
Get a level 3 copy of "Meteorite Satellites"
Get a level 3 copy of "Olive Gun"
Get a level 3 copy of "Homing Loogie"
Get a level 3 copy of "Random Nails"
Get a level 3 copy of "Tiny Spring"
Get a level 3 copy of "Blaster"
Get a level 3 copy of "Fire Beam"
Get a level 3 copy of "Dark Side"
Get a level 3 copy of "Disco"
Obtain the fully upgraded hidden ability "Bonus Bonus"
Obtain the fully upgraded hidden ability "Penetration"
Obtain the fully upgraded hidden ability "Bonus Health"
Obtain the fully upgraded hidden ability "Melee"
Obtain the fully upgraded hidden ability "Power of Observation"
Obtain the fully upgraded hidden ability "Critical Strike"
Obtain the fully upgraded hidden ability "Berserker Mode"
Obtain the fully upgraded hidden ability "Fragility"
Obtain the fully upgraded hidden ability "Efficient Economy"
Obtain the fully upgraded hidden ability "Soul Eating"
Obtain the fully upgraded hidden ability "Time Warp"
Obtain the fully upgraded hidden ability "Damage Reflect"
Obtain the fully upgraded hidden ability "Evasion"
Obtain the fully upgraded hidden ability "Flammable Concoction"
Obtain the fully upgraded hidden ability "Armor"
Get a level 3 copy of "Heretic's Fork"
Obtain the fully upgraded hidden ability "Pricking"
Beat every campaign level