Easy achievement. If you want to get this out of the way quickly, then just play Training mode, and choose each map one-by-one. (Or just the maps you know you haven't played on) Once the map loads up and the announcer says "FIGHT!" then you can exit out to the main menu and go onto the next map.
All 9 maps are below in order:
Danger Room
The Daily Bugle
Metro City
Demon Village
Kattelox Island
Hand Hideout
S.H.I.E.L.D. Helicarrier
Asgard
Tricell Laboratory