This achievement is quite simple and can be unlocked by going to Versus->Custom->LAN Game. Once here you can hit Host Game to create a lobby. Once here choose the Gridiron game mode. Next, go over to the enemy team slots and lock each slot.
Next up you have to have a character from Operation 4 unlocked. The characters needed are:
With one of those characters chosen go ahead and start the match. You should now win each round as soon as it starts. Once you have hit the point limit you will win the game and unlock the achievement.
As a side note, I also unlocked the Shutout achievement while doing this.