huh...i'll tell you! do legendary brawl, and once in the hill, get a shotty and you'll get an overkill easy! otherwise, if brawl is gone today, go to lone wolves and wait for everyone to get weak, then bam!-shoot them in the face. or just play lone wolves and get swords, just throw grenades into the spot where everyone is going to kill each other-that's how i got mine for the ahievement. and for rank, go either into lone wolves or just go into doubles by yourself-you go up MUCH faster when you go in by yourself. otherwise get a good partner so you can win. don't go into doubles by yourself if your not a solid player and cant carry the weight if your team mate sucks. if you aren't that good, i suggest finding a good partner-it'll take some more time, but this way your SURE to get leveled up! Good Luck!