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