Mirza Ghulam Ahmad
That the "Messiah" and "Imam Mahdi" are the same person, and that Islam will defeat the Anti-Christ or Dajjal in a period similar to the period of time it took for nascent Christianity to rise (300 years). Mainstream Muslims believe that Jesus was not crucified, but made to look as though he had been, and that he ascended to heaven from where he will return personally in the flesh to revive Islam.