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.
[Rise of P] Reach the ending.
Collect and play all records.
Find out about the last story of Eugénie.
Find out about the last story of Sophia.
Find out about the last story of Antonia.
Find out about the last story of Venigni.
Learn all gestures.
Find out about the last story of Geppetto.
[Real boy: They all lived happily ever after] Reach the ending.
Collect all normal weapons.
Decipher all cryptic vessels and claim the rewards.
Discover all Trinity Sanctums.
Collect all Legion Arms.
Modify a Legion Arm to its max level.
Play a perfect tune on the piano at Hotel Krat.
Strengthen a special weapon to its max level.
[Free from the puppet string] Reach the ending.
Kill the Nameless Puppet.
Find out about the last story of Simon Manus.
Kill the Awakened God Simon Manus.
Kill Laxasia the Complete.
Kill the Black Rabbit Brotherhood.
Strengthen a normal weapon to its max level.
Kill the Corrupted Parade Master.
Kill the Puppet-Devouring Green Monster.
Activate P-Organ to Phase 5.
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.
Try to assemble a weapon.
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.