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