Here is the full list of all 60 Legend of Grimrock 2 achievements.
Cast 25 spells
Defeat the Viper Roots
Enter the Nexus
Complete the game with hard difficulty setting
Complete the game with old school mode
Defeat a monster with a backstab attack
Kill 250 monsters
Perform 500 melee weapon attacks
Perform 500 missile or throwing weapon attacks
Perform 100 power attacks
Travel 10000 tiles
Dive 250 tiles
Cast 250 Spells
Cast 500 spells
Learn 15 spells
Mix a total of 10 potions
Mix a total of 50 potions
Polymorph 10 times
Find 10 secrets
Find 25 secrets
Find 50 secrets
Find all secrets
Dig up three treasure chests
Dig up all treasure chests
Find 8 skulls
Collect an elemental essence
Collect four elemental essences
Find Bane
Find the pie
Assemble the Meteor Hammer
Catch 25 fish
Open 5 gold locks
Max out a skill
Max out three skills
Visit 10 levels
Visit all levels
Collect and wear archmage's uniform (4 pieces)
Collect and wear rogue's wardrobe (5 pieces)
Collect and wear full set of Crystal armor (6 pieces)
Collect and wear full set of Meteor armor (6 pieces)
Defeat the Summon Stones
Defeat the Ratling Boss
Defeat Herder's Den
Defeat the Wormbound brothers
Defeat the Lindworm
Enter the Shrine of Balance
Open the door to the Archives
Enter the Pyramid of Umas
Open the gate to the Cemetery
Enter the Castle
Enter the Crystal Mines
Summon the Viper Roots in under 6 minutes
Kill a monster by throwing pants at it
Reach level 10 with a farmer
Kill a monster with a single blow
Defeat a Magma Golem
Find the Relic
Deal a killing blow with unarmed attack
Kill a monster by teleporting on it
Complete the game with Ironman and Single-use Crystals modes turned on