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