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Do you have to play every variant of each variant? Like play each variant of Slayer, Each of Assault, etc.?
Yes
And, as the achievement says, you must have at least 3 people or the game will not count. You do not have to do it all in one sitting, either.
and dont forget you need to have a gold account dont be dumb like me and keep wondering why it wasnt unlocking when your subscription expired