This achievement is actually very easy, all you have to do is from the first time you get to play as war, which is in the apocalypse.
Immediately start killing all of the humans. as for the actual enemy's beat them down until you can use the
finisher go grab an item and throw it at 'em.
By the time the apocalypse is done you should already have about 75 kills towards the achievement, then when your going to find Vulgrim kill all the zombies with whatever you can find, do this until you reach your goal.