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