Here is the full list of all 11 The Wonderful End of the World achievements. It takes around 3-4 hours to unlock all of the achievements on Windows.
Obtain 12 A+ grades.
Steal the Orangutan in the Bibliodiscotheque.
Steal a donut in the Bibliodiscotheque.
Complete the Megalopolis level.
Explicitly reset the game, then complete the entire thing in one sitting.
Grab a massive 10,000 or more objects.
Steal a clipper ship in Rice Cake Parade.
Steal the brontosaurus in Bumble Burbs.
Grab 2,500 or more objects.
Devour half the world by finishing 6 of the 12 levels.
Grab 500 or more objects.