Here is the full list of all 123 Cassette Beasts achievements.
Open a door long since thought lost.
Prove your worth to a certain warrior.
Defy all odds in a place between worlds.
Get to 5 hearts with Meredith
Solve the riddle of Morgante's song.
Complete Eugene's quest
Complete Morgante's song
Clear 5 Landkeeper offices
Win a battle while Gambit is active
Complete Felix's quest
Meet Kuneko at 4 altars
Meet Kuneko at 3 altars
Meet Kuneko at 2 altars
Meet Kuneko at 1 altar
Meet Kuneko
Unlock Felix
Obtain an Earth-type bootleg
Complete Kayleigh's quest
Defeat Captain Gladiola
Defeat Heckahedron
Defeat Captain Clee-O
Clear 4 Landkeeper offices
Defeat Babelith
Find a helping hand in a place far away.
Find yourself somewhere far away.
Defeat Poppetox
Defeat 20 Rogue Fusions
Defeat Alice
Win a battle before it starts
Defeat Captain Heather
Clear 3 Landkeeper offices
Defeat Captain Cybil
Obtain the Pumpkin Vine Ball ability
Defeat Lamento Mori
Complete Meredith's quest
Bring Meredith to the mall
Unlock Meredith
Obtain the Diveal Swim ability
Defeat Captain Buffy
Try to sneak past a battler by jumping over their head
Meet the one who dutily attends the stations.
Obtain a Metal-type bootleg
Clear 2 Landkeeper offices
Defeat Captain Lodestein
Obtain the Electromagnetism ability
Start Kayleigh's quest
Defeat 10 Rogue Fusions
Sign up to the Rangers
Defeat 5 Rogue Fusions
Obtain 20 different species
Obtain the Bulletino Dash ability
Investigate a rumour
Obtain a rumour
Clear 1 Landkeeper office
Unlock Eugene
Defeat a Swarm
Defeat a Rogue Fusion
Choose a design for Harbourtown's sign
Obtain 10 different species
Remaster a tape
Complete the tutorial
Obtain the Mothwing Glide ability
Unlock Kayleigh
Obtain Bansheep
Obtain a rare sticker
Obtain Candevil
Defeat an Unstable Fusion
Defeat an Orb Fusion
Defeat 50 Rogue Fusions
Visit every part of New Wirral
Observe 120 different species
Obtain 50 different species
Obtain 100 different species
Obtain 120 different species
Obtain additional data on every species
Obtain a Beast-type bootleg
Obtain a Fire-type bootleg
Obtain a Plastic-type bootleg
Obtain a Plant-type bootleg
Obtain a Water-type bootleg
Obtain a Poison-type bootleg
Obtain an Astral-type bootleg
Obtain an Ice-type bootleg
Obtain a Lightning-type bootleg
Obtain an Air-type bootleg
Obtain a Glass-type bootleg
Obtain a Glitter-type bootleg
Obtain the Averevoir Flight ability
Get the Fusion Radar
Obtain a monster form thought impossible to find.
Unlock Viola
Unlock Barkley
Bring Viola to the shipwreck
Complete Barkley's quest
Complete Viola's quest
Get to 5 hearts with Kayleigh
Get to 5 hearts with Eugene
Get to 5 hearts with Felix
Get to 5 hearts with Barkley
Get to 5 hearts with Viola
Enter a romantic relationship
Reopen every station
Defeat an ancient force brought back to full strength.
Overcome the essence of fusion.
Come face-to-face with a faceless being.
Meet the Travelling Merchant
Defeat Captain Wallace
Defeat Captain Skip
Defeat Captain Zedd
Defeat Captain Judas
Defeat Captain Penny Dreadful
Defeat Captain Codey
Defeat Ianthe and become a Ranger Captain
Help Sunny start a new life
Help Hoylake with his research
Defeat a ghost
Complete Frankie's training
Complete Vin's training
Complete 5 noticeboard quests
Complete 20 noticeboard quests
Complete 50 noticeboard quests
Complete 100 noticeboard quests
Win a battle while ghostly