For me the only thing that worked was fully charged melee kills. So fifty fully charged punches. Frustrating is right. I hope it's bugged so that any kills inside the bubble count because otherwise its just wrong.
I've done it with the armamentarium in the dark beyond. each 2 grenades got 10-15 kills. then 1 kill from a punch. Was quite fast.
Edit: Top page without any gif.
 
	 
				 
 
		 
 
		
 I miss it dearly.
 I miss it dearly. 
 
		