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.
Recover your mental energy with a Dream Fluff
Completely fill your Astral Wallet
Acquire all Upgrades
Complete Gisu's Psychoseismometer Quest
Throw a Regret's anvil at another enemy
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS
Achieve Rank 100
Return to where it all started
Find all Figments
Tag all Emotional Baggage
Crack all Vaults
Purchase all Pins
Dissolve the Deluge of Grulovia
Pyro 3 enemies at once
Frequent Fatherland Follies
Break all 3 Gramaphones in Fatherland Follies
Soothe Lucrecia's Lament
Empty Bob's Bottles
Purchase all Otto Shot Filters
Max out your Dream Fluff capacity
Peruse Cassie's Collection
Max out your PSI Pop capacity
Discover the Astralathe
Raid the Tomb of the Sharkophagus
Repair Ford Fractured
Treat Ford's Follicles
Achieve Rank 50
Bowl Strike City
Revisit a brain through the Collective Unconscious
Plate Compton's Cookoff
Throw a Judge's gavel back at him
Equip 3 Pins at once
Complete Lili's Request
Complete Queepie Quest
Help Dion Setup Aquatodome
Upgrade to the Astral Wallet
Find the Family Camp
Fully upgrade a Badge
Deliver Cruller's Correspondence
Complete PSI King's Sensorium
Consume a PSI Pop to restore some mental energy
Find the real Panic Attack during his Phantom attack
Tune in to a Stray Thought
Take a photo with the Otto Shot
Visit the Collective Unconscious
Shut Down the Luctopus
Cool Hollis' Hot Streak
Upgrade your first Badge
Make a connection in Hollis' Classroom
Achieve Rank 10
Receive your first assignment
Equip your first Pin
Combine PSI Cards with a PSI Core at the Otto-Matic
Talk to Milla in her Office
Achieve Rank 2
Navigate Loboto's Labyrinth
TK throw an object to stun an enemy