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