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