If I recall correctly, this is the "Kill the entire enemy team within 10 seconds" challenge. There is another qualifier to completing the challenge, as well - there must be 4 or more people on the opposing team.
Regardless of the game mode you use, keep a Predator in your streak rewards. In fact, what you may want to do is focus on scoring the 1000 Predator kills prestige challenge. I can almost guarantee that if you score 1000 kills with a Predator at least once you will kill the entire enemy team with a single Predator hit.
I've done it a bunch of times.