Originally Posted by Married2Mary
i dont see how it would take around 50 unless you did something wrong. the way i described is the correct method so all that crying about it being glitched is over. mad mac even found a certain way and level to get it. i send tailz a pm to change it on the achievement guide page but im pretty he or she is not worried about dark void anymore but this is the real deal ladies and gentlemen.
I played through the first level 3-4 times, killed everyone I could in the level with grenades exploding in the air.
After that, while I wrapped up on 2-4, during all of the points where I had to fight on the ground I used this method and it popped about halfway through my farming. I'm absolutely sure it took more than 20, but 50 may have been an exaggeration.
Also, a few of the grenades exploded about chest-level with the enemies, so that may have been an issue. I don't know if they were supposed to explode over their heads, but that could very well have been the problem.