I am very annoyed by this!
I got all of the achievements for the Crimson DLC except this one, even though I have met all requirements (20 foot stomp kills with mantis in Crimson DLC playlist). I got 24 foot stomp kills on Shatter legitimately and sstill nothing. I checked my stats on waypoint. DOes anybody have any news about this? Will it get fixed soon? Can I ever get the achievement,?