I've been playing this game since Beta, and I have literally never seen someone get this medal.
I've seen two or three people with the medal in their profiles, but I know for a fact that these people farmed for it by matching teams of friends in 6s.
For those of you who don't know, the medal is rewarded upon the rapid killing of 4 enemies.
Why does Bungo put medals like this, Phantom, and Relentless in the game, when nobody can get them without cheating?
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Try using a Stormcaller Warlock, it helps. Like, it helps a lot. I've gotten like 3+ in the past week I believe.