Mahdi is the future political and Islamic savior of mankind that will forcefully convert the world to Islam, according to both Sunni and Shia schools. He will rule for 7, 9, or 19 years, depending on the various interpretations of Muslim scholars.
He will unite the Muslims into a theocratic confederation and will establish the Islamic Caliphate.
Similarities between the Mahdi and the Antichrist
Just to name a few similarities, both will sign a final peace covenant with a Jew of priestly lineage for 7 years; Both will persecute Jews and the religious opponents who denounce them; Both will come at a time of chaos; Both will institute a global religion; Both will have supernatural powers to convert people to their world religion; Both of them will divide their loot among their followers (As found in Daniel 11:24).