After finishing the campaign and finding all of the hidden hack levels, I had two achievements left. This and:
I found that the Story Mode hack levels also counted, so you need to do the following 5 levels to unlock this achievement.
To access these, go to the Main Menu and select Play Minigame.Arenas:
Mega Arena (Mine actually popped after this one, but some people reported they had to finish Giga Arena as well to unlock it.)
You may also do the following to count towards the 10 if you don't have all of those unlocked:Mazes: