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