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.
Find out about the last story of Sophia.
Collect and play all records.
Find out about the last story of Eugénie.
[Free from the puppet string] Reach the ending.
Kill the Nameless Puppet.
Find out about the last story of Venigni.
Collect all normal weapons.
Decipher all cryptic vessels and claim the rewards.
Discover all Trinity Sanctums.
Learn all gestures.
Collect all Legion Arms.
Activate P-Organ to Phase 5.
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.
Modify a Legion Arm to its max level.
Find out about the last story of Antonia.
Strengthen a special weapon to its max level.
Kill Laxasia the Complete.
Strengthen a normal 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 Fallen Archbishop Andreus.
Kill the Eldest of the Black Rabbit Brotherhood.
Kill King’s Flame, Fuoco.
Kill the Scrapped Watchman.
Try to assemble a weapon.
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.