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 Geppetto.
[Real boy: They all lived happily ever after] Reach the ending.
Collect all special weapons.
[Free from the puppet string] Reach the ending.
Collect and play all records.
Find out about the last story of Eugénie.
Collect all normal weapons.
Try to assemble a weapon.
Learn all gestures.
Modify a Legion Arm to its max level.
Collect all Legion Arms.
Strengthen a normal weapon to its max level.
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.
Find out about the last story of Simon Manus.
Kill the Awakened God Simon Manus.
Find out about the last story of Antonia.
Kill Laxasia the Complete.
Decipher all cryptic vessels and claim the rewards.
Find out about the last story of Venigni.
Activate P-Organ to Phase 5.
Discover all Trinity Sanctums.
Strengthen a special weapon to its max level.
Kill the Black Rabbit Brotherhood.
Kill the Corrupted Parade Master.
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.
Kill a Stalker.
Tell a lie in front of Hotel Krat Entrance.
Kill the Parade Master.
Repair a Stargazer.
Destroy an enemy’s weapon with a perfect guard.
Deliver a successful Fatal Attack.