The belief in the Antichrist. An Antichristian is the opposite of a Christian. They deny Jesus's teachings of forgiveness and righteousness. They will deliberately take Christianity's holy teachings and alter it to an Antichristian following, like "forgive your enemies" will become "hate those who aren't your enemies" or "hate your enemies". Antichristianity and Satanism are not the same thing so do not confuse the two because Antichristians don't worship the devil, they have no real path to anything. They can twist Jesus's image into an evil mastermind, but that's rare.
Christian: Have you accepted Jesus as your savior?
Antichristian: Jesus is actually sick minded and demented as well as the savior of Antichristianity. That's why I like him
Christian: Jesus tells us to love all that surround us
Antichristian: No fuckhead, he actually wants us to hate everyone that surrounds us, they get in our way. We don't need the stupid fuckers, especially YOU