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