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