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