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