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