Very situational, but very doable. Select the Team Play option when finding a match and vote for rounds of Warpath and Soul Harvest, as well as Team Deathmatch.
This just has to be any number of kills above 1 in quick succession; a double kill is all you need. If you manage to get the demon rune, from there just hold L2 and get an unlucky group of enemies, no real strategy here besides having good aim during the charge attack, its an instant kill so keep charging into more victims. I would say sneak around while cloaked to find a group of unaware chumps but luck is just as effective.