There are 12 maps in total. The first nine can be found under any Objective game type and they are:
The final three can be found under the Mob Blobs game type, and they are:
Finishing a match on all of these maps will unlock the achievement. Something to note is I recommend doing all of these with only one controller and no guests logged in, because this wouldn't unlock when I had a few guests playing despite all other achievements unlocking with them.