Ive seen a video, and it might be getting multiple super kills IN A SINGLE LIFE! Based from the video, the guy got 7 super kills in one life, i think. (here's the link: https://www.youtube.com/watch?v=1bC1Z4_yTrI) Time stamp 8:32
I was wondering this myself, after getting the medal, my best guess is either getting four people with a single super or a triple kill with a super.
Personally I think that it is awarded for killing four people with one super, as my kills were not consecutive.
It also could be getting X amount of people in a game with a super, but we would need more information.
Hope this helps, cheers