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