Here is the full list of all 42 Lies of P achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Find out about the last story of Sophia.
Play a perfect tune on the piano at Hotel Krat.
[Rise of P] Reach the ending.
Kill the Nameless Puppet.
Collect all Legion Arms.
Find out about the last story of Venigni.
Discover all Trinity Sanctums.
Find out about the last story of Simon Manus.
Kill the Awakened God Simon Manus.
Learn all gestures.
Find out about the last story of Antonia.
Kill Laxasia the Complete.
Kill the Black Rabbit Brotherhood.
Strengthen a normal weapon to its max level.
Kill the Corrupted Parade Master.
Activate P-Organ to Phase 5.
Strengthen a special weapon to its max level.
Modify a Legion Arm to its max level.
Kill the Puppet-Devouring Green Monster.
Kill Champion Victor.
Kill all types of Dimensional Butterflies.
Kill Romeo, King of Puppets.
Harvest Gold Coin Fruit.
Kill the Eldest of the Black Rabbit Brotherhood.
Kill the Fallen Archbishop Andreus.
Kill King’s Flame, Fuoco.
Kill the Scrapped Watchman.
Destroy an enemy’s weapon with a perfect guard.
Try to assemble a weapon.
Kill a Stalker.
Tell a lie in front of Hotel Krat Entrance.
Kill the Parade Master.
Repair a Stargazer.
Deliver a successful Fatal Attack.
[Real boy: They all lived happily ever after] Reach the ending.
[Free from the puppet string] Reach the ending.
Collect all special weapons.
Collect all normal weapons.
Collect and play all records.
Decipher all cryptic vessels and claim the rewards.
Find out about the last story of Geppetto.
Find out about the last story of Eugénie.