The antichrist is a hypothetical figure who poses the greatest possible ideological threat, an exploit against which the overwhelming majority of Christianity's (worldly) resources and personnel cannot be secured. The popular theory is, that individual's public actions would trigger the ultimate 'evaporative cooling' event. Everybody who doesn't really believe, everybody who just checks "christian" on the census form and shows up to church for the social network and the pancakes, will stop doing so.

That's nice, but I'm Jewish ;-). Or in other words, the very nature of an "antichrist" pins you to opposing one kind of religion in specific, and also pins you to moral positions you probably don't want to take. It's the ultimate sin of privileging the hypothesis: you've assumed it's a Christian world you have to persuade away from their Christianity.

(In real life, I would argue the greatest utility to be gained from deconversions right now is in the Muslim world, where one currently finds the greatest amount of religious violence over the smallest differences. You could tell me to go become the Anti-Muhammad, but again, I'm already Jewish.)

Remember, the Antichrist is also puppy-kickingly evil. You don't hate puppies, do you? Then why are you signing up for a role that outright requires you to kick them?

Are you sure there's not some other evil villain you'd prefer to be?