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