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