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