Here is the full list of all 48 The Messenger achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Beat the game
Defeat Phantom
Complete the Melody
Survive the Corrupted Future chase
Enter all areas of the world
Defeat the Demon King
Kill a green demon in a single hit
Buy all upgrades from the shop
Complete the Elemental Skylands scenario
Rescue all Phobekins
Run on lava
Receive the Key of Love
Make it out of the underwater labyrinth
Bump on a few flowers in Rivière Turquoise
Ride Manfred around the world back to where it all started
Defeat the Demon General
Defeat the Sky Serpent
Time travel to the future
Defeat the Arcane Golem
Get to the top of the mountain
Defeat Colos & Suses
Defeat the Queen of Quills
Execute 15 Cloudsteps without landing or clinging to a wall
Defeat the Emerald Golem
Jump down the big waterfall in Bamboo Creek
Defeat the Necromancer
Meet Quarble
Buy the Swim Dash upgrade from the shop
Buy five upgrades in the shop
Destroy a Big Time Shard
Destroy your first Power Seal
Attack your first enemy projectile
Beat the intro without dying
Make it through Dark Cave without the 'Power of True Sight'
Destroy all Power Seals
Be lectured on happiness
Be lectured on the power of stories
Be lectured on the inner child
Keep a windmill shuriken going for 15 seconds
Make it from the beginning of the game to beating the Queen of Quills with zero deaths
Defeat Octo
Defeat the Voodoo Totem
Defeat the Demon General... again
Win the race with a perfect score
Make your first purchase at the Craftman's Corner
Meet the voodoo mask
Unclog the Money Sink
Accept 'THE DEAL'