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