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