If “the Antichrist” is really a single entity and not the many who oppose Christianity while claiming to be Christion as in the letters of John, then it is surely Mohammed and his hellific progeny. What fits better than Islam? even to the conquest of Jerusalem and the proclamation therefrom of the return of the messiah (mahdi) which many, perhaps most will by then worship, at least most in the old civilized world, Moslem Europe and perhaps shariah America. So far, at least, China appears to be exempt and may be the last stronghold of Christianity.
Also, I'm not at all convinced that "antichrist" referred by John in 1st and 2nd John is the same thing as the "Beast" referred to by John in Revelation. We do know that the strange beasts identified in Daniel and again referred to in Revelation represent different civilizations or groups according to the Angel who interpreted the visions to Daniel. I tend to think the Beast is the same and Islam fits the description better than anything.