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