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