Here is the full list of all 57 Psychonauts 2 achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Purchase all Pins
Acquire all Upgrades
Max out your PSI Pop capacity
Purchase all Otto Shot Filters
Complete Gisu's Psychoseismometer Quest
Find the real Panic Attack during his Phantom attack
Complete Lili's Request
Achieve Rank 100
Completely fill your Astral Wallet
Tag all Emotional Baggage
Find all Figments
Crack all Vaults
Break all 3 Gramaphones in Fatherland Follies
Recover your mental energy with a Dream Fluff
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Return to where it all started
Complete Queepie Quest
Max out your Dream Fluff capacity
Dissolve the Deluge of Grulovia
Frequent Fatherland Follies
Soothe Lucrecia's Lament
Peruse Cassie's Collection
Achieve Rank 50
Empty Bob's Bottles
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Treat Ford's Follicles
Repair Ford Fractured
Deliver Cruller's Correspondence
Throw a Regret's anvil at another enemy
Complete PSI King's Sensorium
Pyro 3 enemies at once
Take a photo with the Otto Shot
Tune in to a Stray Thought
Upgrade to the Astral Wallet
Bowl Strike City
Fully upgrade a Badge
Plate Compton's Cookoff
Throw a Judge's gavel back at him
Equip 3 Pins at once
Help Dion Setup Aquatodome
Find the Family Camp
Talk to Milla in her Office
Revisit a brain through the Collective Unconscious
Visit the Collective Unconscious
Cool Hollis' Hot Streak
Shut Down the Luctopus
Achieve Rank 10
Make a connection in Hollis' Classroom
Receive your first assignment
Upgrade your first Badge
Equip your first Pin
Achieve Rank 2
Combine PSI Cards with a PSI Core at the Otto-Matic
Navigate Loboto's Labyrinth
Consume a PSI Pop to restore some mental energy
TK throw an object to stun an enemy