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