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
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Return to where it all started
Achieve Rank 100
Tag all Emotional Baggage
Find all Figments
Dissolve the Deluge of Grulovia
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
Take a photo with the Otto Shot
Purchase all Pins
Peruse Cassie's Collection
Equip 3 Pins at once
Empty Bob's Bottles
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Repair Ford Fractured
Treat Ford's Follicles
Purchase all Otto Shot Filters
Bowl Strike City
Plate Compton's Cookoff
Achieve Rank 50
Throw a Judge's gavel back at him
Complete Lili's Request
Complete Gisu's Psychoseismometer Quest
Max out your Dream Fluff capacity
Deliver Cruller's Correspondence
Complete PSI King's Sensorium
Find the real Panic Attack during his Phantom attack
Max out your PSI Pop capacity
Tune in to a Stray Thought
Complete Queepie Quest
Fully upgrade a Badge
Help Dion Setup Aquatodome
Upgrade to the Astral Wallet
Find the Family Camp
Equip your first Pin
Throw a Regret's anvil at another enemy
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
Talk to Milla in her Office
Upgrade your first Badge
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