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