There is no other Head of the Church but the Lord Jesus Christ (Eph 1:22; Col 1:18): nor can the Pope of Rome, in any sense be head thereof; but is that Antichrist, that man of sin and son of perdition, that exalteth himself in the Church against Christ, and all that is called God (Mat 23:8-10; 2 Thes 2:3-4, 8-9; Rev 13:6).
WCF 25:6
[Antichrist] shall be a master of sin and all iniquity, and yet will retain the name and appearance of Christ and call himself “most holy one; vicar of God; head of the Church,” and persecute all who will not obey him… the pope more than fits this description. — Martin Luther
Do still protestants believe that the pope is the antichrist?