Warhammer 40,000: Dawn of War II

This one is very hard to get without boosting, but thankfully its easily boosted. What you have to do is go into a public Free For All match and hold 5 victory points at once. There are 7 on each FFA map but with 5 other players its a tough achievement.

However much like King of the Hill you only need one other player to set up a matched and boost so this is probably your best bet.