The title pretty much says it all. I've played prime almost exclusively for the past few days with a heavy focus on kill steaks and gotten 0 medals. I have almost 13k kills with reaper aura, ~85 wins. Twice as many as the other "triumphant" triumphs. It shouldn't take that long and it should be something you can achieve without tanking your entire play style. If you keep such things you should be able to review my combat logs from the past few days. It is all Gambit prime.