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