How do you beat gears???

Well, i think i beat gears of war 2 but im running into a problem.

I do the last level (The one were you kill the infected brumak with the hammer of dawn) and then it goes to the credits, i leave because...im not sittinr through credits. I come back and its on main screen, i go into campaign and it wants me to beat the level again? And i dont have the achievment for beating it?

Anyone know what the heck your supposed to do>?

 

Protip: Sit through the credits and curse the makers of the game. (Not even joking)

 

Haha why? I want the achievement!


Off-topic: Im getting live tonight. :laugh:

 

Bump. Still not resolved.