I think the Whore is the Vatican City/Roman Catholic Church.
It is said the woman is the whore and the seven heads of the beast are the seven mountains it is located on. This woman is mentioned as te mystery Babylon. Vatican city is situated on the seven hills ---- Mystery Babylon (Rev17:18,19)

Babylon is a code word for Rome. Even in Acts Peter refers to Rome as Babylon. It is used that way six times in the last book of the Bible [four of the six are in chapters 17 and 18] and in extra-biblical works such as Syblling Oracles (5, 159f.), and Apocalypse of Baruch (ii, 1), and 4 Esdras (3:1).

Her pope enthroned in Rome claims to be the exclusive representative of God, the Vicar of Christ. Rome is the headquarters of the Roman Catholic Church, and in that too she is unique.

Roman Church slaughtered Jews by the thousands--more than pagan Rome ever did. Many Christians were charged as heretics and martyred for Church. She is drunk with the blood of saints it is said in the Revelation Chapter.

John provides many characteristics to limit the identification to Rome alone.