I was in a game where a fully powered up Juggernaut and Pestilence attacked each other but didn't get the achievement. Others in the game claim to have received it but I and a couple others didn't get it. We all planned it and openly claimed Plaguebearer and Juggernaut. Is there a reason for this? Another thing that may be related to it is when I got achievements I didn't get the popup in the game on screen but I would receive it in steam after I had left the match.
Thanks, A Townie.