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