Here is the full list of all 24 Owlboy achievements worth 1,000 gamerscore. It takes around 10-12 hours to unlock all of the achievements on Xbox One.
Master Owlboy in all possible ways
Beat Geddy 1000 times
Played Otus's song on Bomboman's drums
Learn how to cope with the heat in Toby's hot spring
Unlock every trinket from Buccanary's shop
Collect all Buccanary coins
Collect every Buccanary coin from all zones
Collect the Golden disks
Master trinket collection at Buccanary's!
Beat the game
What are you doing, Owlboy?!
Listen to the shell near the old ruins
Clear the Boguin's Cannon Challenge
Enjoy your explosive surprise after rescuing the Boguin Brothers
Twig joins your team!
Defeated the Molten Guardian
Defeat the Security System
Survived the Destruction of Advent
Escaped the Frog Guardian
Alphonse joins your team!
Obtain the Strange Device
Try to report to Asio at the first sign of trouble
Throw Geddy into the clouds! How rude!
Geddy joins your team!