Here is the full list of all 39 Rainbow Billy: The Curse of the Leviathan achievements.
Break the Curse of the Leviathan and save the World.
Accept your other self and befriend Shadow Billy.
Collect ALL Thought Upgrades!
Collect 75 Thoughts.
Get reprimanded for punching barrel-kind.
Hear each and every one of the The Confessor's secrets.
Raise 30 creatures' friendships to Level 2!
Fast travel between two distant areas of the World.
Glide using the Billy-Copter for more than 5 straight seconds!
Peek through the window...
Face your fears and befriend Calypso.
Talk to all Kickstarter Backers characters!
Own 500 coins or more.
Collect 50 Thoughts.
Discover the broken warp pipe.
Collect 25 Thoughts.
Fight toxic masculinity and befriend Dragalant.
Flawlessly complete a difficult "Dodge" attack minigame!
Flawlessly complete a difficult "Paddle" attack minigame!
Flawlessly complete 50 attack minigames!
Catch 10 non-gummi items while fishing.
Raise 5 creatures' friendships to Level 2!
Discover Disco Broccoli!
Dig up 15 buried treasures.
Collect 10 Thoughts.
Recolor five colors in one blow!
Flawlessly complete a difficult "Circle" attack minigame!
Catch three different objects in one fishing session!
Destroy 25 Objects!
Convert a Thought into a Figment of Imagination!Service.
Flawlessly complete a difficult "Slots" attack minigame!
Flawlessly complete a difficult "Line" attack minigame!
Listen to Friend-Ship whistle for more than 5 straight seconds.
Raise 20 creatures' friendships to Level 3!
Raise 40 creatures' friendships to Level 3!
Befriend all creatures.
Raise ALL creatures' friendships to Level 3!
Catch at least one of each kind of fish!
Climb to the highest point in each area of the World.