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