If you have the Founder or Ultimate God pack (with all gods unlocked), this achievement is trivial using Nu Wa. Her Ultimate (
) ability automatically hits every enemy god on the field (all 3 or all 5, depending on match type), no matter where they are.
In short: Pick Nu Wa. Hit
. Achievement unlocked.
(One last note -- remember, like with all other achievements in this game, you have to be playing in a PvP match. Co-op matches against the computer don't count for achievements).