Here is the full list of all 52 Letter Quest: Grimm's Journey achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Earn 40 crystal stars
Earn 120 stars
Do 100 critical attacks
Purchase 10 potions
Spell 2000 words
Fill the entire board with duplicator tiles
Swap all letters 50 times
Purchase 5 books
Purchase 30 upgrades
Spend 25000 gems
Earn 99 stars
Defeat 250 monsters
Earn 20 crystal stars
Fill the entire board with plague tiles
Bust apart 100 gem piles.
Use 2500 vowels
Complete 50 quests
Dodge 50 attacks
Use 5000 letters
Spell 200 double-letter words (ex: 'bubble')
Use 100 crystals
Reach max level with one book
Open a treasure chest with no incorrect guesses
Defeat 5 monsters with exact damage
Earn 15000 gems
Earn 1000 book XP
Spell 25 palindromes
Deal 25000 damage
Spell the word BANDITS
Lose from taking tile damage
Use 500 corner letters
Take 10000 damage
Spell 5 eight-letter words
Spell 50 six-letter words
Spell a word that contains two 'Y's
Earn 29 stars
Finish a stage with full health
Open 10 treasure chests
Spell a word containing two or more crystals
Deal 10000 damage
Spell 10 seven-letter words
Use 500 letters from the top row
Use an entire row in one word 3 times
Use 25 plague tiles
Spell 3 words with no vowels
Spell a word that does zero damage
Leave a monster with only one health
Beat a stage with only 1 health remaining
Spell the word BACON
Spell 3000 words
Purchase 50 merchant items in battle
Fail to open 20 treasure chests