Antagonist
Character Role Analysis
The Lottery
So, if we're going with something as general as the village to be "The Lottery's" protagonist, then the antagonist is certainly the lottery itself.
The villagers seem completely unconscious of their own power over the lottery; they're afraid of the black box, and both fascinated and fearful at the ritual of the lottery itself. They risk death every year, but they participate eagerly in killing their fellows when they realize, relieved, that they're time's not up yet.
The tradition of the lottery is so powerful, and so beyond logic, that few villagers can even imagine breaking it. The lottery promises protection for the villagers (or at least, that's what Old Man Warner keeps blaring), but really, its perpetuation undercuts the family and community ties that tradition is supposed to protect.