This is another achievement that just takes dedication. Attack and defeat all the factions on the map.
It is probably easier to do it early in the game, but I actually went postal on my opponents on the last map - Vancouver. I just held off on beating the last town square of the main opponent until I had beaten all the rest.
This was also the map where I finished the achievements Assembly Line, Omegaman, Fuzzy Wuzzies, I see the Medicine, Year's Supply and Nerdcore. The map is just so huge that it works well here.