Beat mission in co op start to finish no achievement

#1XtremeWRATH360Posted 3/14/2013 7:46:01 PM
Anyone have any ideas as to why it didn't unlock?
We started at the start of Forerunner and went through the whole mission and once we beat it no achievement.
Juan is........NUMBER 1!
#2Pyronix337Posted 3/15/2013 12:26:23 AM
Are you referring to the achievement Bropocalypse? Were you playing it on a high enough difficulty (has to be on Heroic or harder)?