If the pope is God's represenative on Earth what is the difference between the antiChrist and the anti-pope?

The Pope is not God's representative. The Scriptures are...the Holy Bible. God needs no vicar. He is our priest, our mediator, our savior and our God. Anyone who is the anti-Christ is simply someone who does not confess Him but denies Him. There is no specific "Antichrist" but many of them over the centuries.