It’s a crazy amount of proximity kills from perfect fifth explosions (or burns, forget which) that count for it. It’s dumb and it doesn’t quite trigger right half the time. Think you need over 200 of them to complete it too. Good luck man, that one can be trying EDIT: so I’m a bonehead. Wrong weapon, lol. Sorry bout that. Might be a bug then if it’s sky burners. It’s also possible that the cabal there are being flagged as something else, like nightmares. Not sure. You could test it in the Cabal zones of EDZ to see if you gain progress at all, though I don’t know if there was any other specific things about skyburners, or if it had a ridiculous amount of kills.