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