Here is the full list of all 33 Runner3 achievements.
Got 'em All!
Finish all 9 Impossible Levels!
Witness something creepy.
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?
Buy a bunch of new digs!
Head off the Beaten Path...
Better out than in...
Defeat Spookyland's Bosses!
Defeat The Caves' Bosses!
Buy a bunch of Capes!
Make it to the end of an Impossible Level!
Collect all Golds and Gems and finish an Impossible Level!
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!
Buy a bunch of Accessories!
Get a Special+!
Get a Special+ and a Perfect+ in any Level!
Get a Special, a Perfect, and one Bullseye in any Level!
Get a Special!
Get a Special AND a Perfect in any one level!
Defeat The Great Outdoors' Boss!
Get a Perfect+!
Get a Perfect!
Checkpoints? Who needs 'em!
Unlock EVERYTHING!