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