Here is the full list of all 16 Newfound Courage achievements.
Fed Jake and Alex some apples.
Make Alex jump off Deadworld too many times.
Make Alex eat sweets till he gets a stomach ache.
Clean up the last book the Blank Sending throws.
Complete the Lorebook.
Complete Newfound Courage.
Complete the entire Return to Otherwhere DLC.
Fight to the death in the Silverpine Arena.