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