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