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