Here is the full list of all 33 Runner3 achievements.
Got 'em All!
Finish all 9 Impossible Levels!
Witness something creepy.
Get all your friends over for some GRILLINS!
Head off the Beaten Path...
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?
Bonk the Timbletot!
Defeat Machineland's Boss!
Defeat The Great Outdoors' Boss!
Invite a friend to the BBQ!
Defeat Spookyland's Bosses!
Buy a bunch of Accessories!
Buy a bunch of Capes!
Defeat The Caves' Bosses!
Better out than in...
Get a Special in each Standard Level in any World!
Defeat Foodland's Boss!
Get a Perfect 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!
Get a Special AND a Perfect in any one level!
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!
Checkpoints? Who needs 'em!
Unlock EVERYTHING!
Buy a bunch of new digs!