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