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.
Beat a stage with only 1 health remaining
Purchase 50 merchant items in battle
Spell 3000 words
Open a treasure chest with no incorrect guesses
Fail to open 20 treasure chests
Purchase 10 potions
Spell a word that contains two 'Y's
Swap all letters 50 times
Spell the word BANDITS
Earn 40 crystal stars
Earn 120 stars
Fill the entire board with duplicator tiles
Fill the entire board with plague tiles
Lose from taking tile damage
Earn 99 stars
Spell 2000 words
Defeat 250 monsters
Purchase 30 upgrades
Spell 25 palindromes
Spell the word BACON
Bust apart 100 gem piles.
Do 100 critical attacks
Spell 200 double-letter words (ex: 'bubble')
Earn 20 crystal stars
Complete 50 quests
Use 2500 vowels
Purchase 5 books
Spend 25000 gems
Reach max level with one book
Dodge 50 attacks
Use 5000 letters
Use 100 crystals
Use an entire row in one word 3 times
Earn 1000 book XP
Spell a word containing two or more crystals
Open 10 treasure chests
Earn 15000 gems
Deal 25000 damage
Spell 3 words with no vowels
Take 10000 damage
Use 500 corner letters
Finish a stage with full health
Spell 50 six-letter words
Earn 29 stars
Spell 5 eight-letter words
Use 500 letters from the top row
Deal 10000 damage
Spell 10 seven-letter words
Defeat 5 monsters with exact damage
Use 25 plague tiles
Spell a word that does zero damage
Leave a monster with only one health