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