After finishing the campaign and finding all of the hidden hack levels, I only had 2 achievements left.
I found that the Story Mode hack levels also counted, so you need to do the following 10 levels to unlock this achievement.
To access these, go to the Main Menu and select Play Minigame.Arenas:
Mega Maze (Mine popped after this one, but some people reported that they had to do Giga Maze as well.)
You may also do the following to count towards the 15 if you don't have all of those unlocked:Teleports: