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
Acquire all Upgrades
Find all Figments
Tag all Emotional Baggage
Achieve Rank 100
Crack all Vaults
Purchase all Otto Shot Filters
Complete Gisu's Psychoseismometer Quest
Purchase all Pins
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Break all 3 Gramaphones in Fatherland Follies
Max out your Dream Fluff capacity
Max out your PSI Pop capacity
Completely fill your Astral Wallet
Take a photo with the Otto Shot
Complete Queepie Quest
Complete Lili's Request
Return to where it all started
Dissolve the Deluge of Grulovia
Frequent Fatherland Follies
Soothe Lucrecia's Lament
Peruse Cassie's Collection
Empty Bob's Bottles
Achieve Rank 50
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Repair Ford Fractured
Deliver Cruller's Correspondence
Pyro 3 enemies at once
Complete PSI King's Sensorium
Recover your mental energy with a Dream Fluff
Find the real Panic Attack during his Phantom attack
Tune in to a Stray Thought
Equip 3 Pins at once
Bowl Strike City
Plate Compton's Cookoff
Throw a Judge's gavel back at him
Treat Ford's Follicles
Upgrade to the Astral Wallet
Help Dion Setup Aquatodome
Find the Family Camp
Talk to Milla in her Office
Revisit a brain through the Collective Unconscious
Visit the Collective Unconscious
Cool Hollis' Hot Streak
Shut Down the Luctopus
Fully upgrade a Badge
Make a connection in Hollis' Classroom
Achieve Rank 10
Upgrade your first Badge
Receive your first assignment
Equip your first Pin
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