The Bible says:
The antichrist has been here since the first century (1John 2:18, 1John 4:3)
The antichrist will still be here when Jesus Christ returns (2 Thessalonians 2:8)
The antichrist cannot be a single personality because the antichrist has been here almost 2000 years so far.
The antichrist must be an office or a position of authority
The antichrist will not occupy a temple in Jerusalem but will occupy a place amongst what might initially appear to be the body of Christ. The antichrist will sit as the head of this false church. (2 Thessalonians 2:4)
There is only one possibility that can fulfill all these prophesies. And the pope is the only possible position that fulfills all of these scriptural prophesies.