The method I'm posting is a boosting method, and will allow you to get this achievement while you sleep and go to work/ school. My friend Maathyas came out with this idea and it had worked perfectly.
Please do not leave a negative comment if you're not into boosting. I'm just trying to help people who want to get this fast.
- 4 people (including yourself), each with second controllers
- to leave your xbox 360 on while you're away
- Social Xbox Live
Decide on who'd get the achievement first. Out of the three persons who're not, two should login with their second controllers as guests at the main menu. The person without a guest should start a lobby and invite the two of them to make it a team of five punching bags. Start the game and inform all in the party of the loaded map.
Now, the person who's getting the achievement should form a team of five, which should include four bots. Nine out of ten times, he/ she should be able to join the friendly game. If the map isn't correct, simply quit and re-search.
When all are in the same game, leave your xbox on, turn off your TV, and all can now go do their own things. With a team of five dummies vs a team of one dummy plus four insane bots, it's pretty obvious who'd win the rounds.
After each match/ map, the parties involved will automatically rematch as long as neither party leaves the lobby. This makes it impossible for any randoms to disrupt the boosting.
Based on my experience, the team with four bots takes on average 10-15 minutes to win a map. Meaning it'd take about five to seven hours for the bots to win on all the maps for the person who's getting the achievement.
(Some maps take longer because the bots seem to have trouble finding their way to the nodes, especially when it's located on the upper floor.)
As such, do so at about 10:00pm at night, and then go to bed. Wake up the next morning, check that you've gotten the achievement, and redo the process for the next person while you go to school/ work. Depending on how fast you get it and switch the teams around, you should be getting the achievement in about two days of "dedicated not-playing".
As it is, I did this method with three of my friends last night, and two of us have gotten it, and one is two maps short of doing so as we checked this morning.
With this, you won't need to worry about maps cycle. Just leave the box on for some time and the achievement will unlock without you having to fire a single shot.
PS: See comments for alternative boosting method involving similar setup.