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