Here is the full list of all 33 Runner3 achievements.
Finish all 9 Impossible Levels!
Unlock EVERYTHING!
Got 'em All!
Collect all the Narrator's Puppetshow Puppets!
Witness something creepy.
Get all your friends over for some GRILLINS!
Bonk the Timbletot!
Defeat Machineland's Boss!
Get all the Gildans!
Defeat the Jungle Ruins' Boss!
Go exploring in the Retro World. Maybe you'll find a cute secret?
Defeat The Caves' Bosses!
Buy a bunch of new digs!
Buy a bunch of Capes!
Defeat Spookyland's Bosses!
Get a Special in each Standard Level in any World!
Better out than in...
Get a Perfect in each Standard Level in any World!
Buy a bunch of Accessories!
Defeat The Great Outdoors' Boss!
Checkpoints? Who needs 'em!
Collect all Golds and Gems and finish an Impossible Level!
Invite a friend to the BBQ!
Get a Special+!
Get a Special, a Perfect, and one Bullseye in any Level!
Get a Special+ and a Perfect+ in any Level!
Head off the Beaten Path...
Defeat Foodland's Boss!
Make it to the end of an Impossible Level!
Get a Perfect+!
Get a Special!
Get a Special AND a Perfect in any one level!
Get a Perfect!