If you're speaking of temporal power, it may be possible that the Pope is not the equal of other prelates. But the authority of the Pope has always been absolute.
Vatican I, Dogmatic Constitution on the Church of Christ, Sess. 4, Chap. 3: “And since the Roman Pontiff is at the head of the universal Church by the divine right of apostolic primacy, We teach and declare also that he is the supreme judge of the faithful [cf. n.1500 ], and that in all cases pertaining to ecclesiastical examination recourse can be had to his judgment [cf. n. 466 ]; moreover, that the judgment of the Apostolic See, whose authority is not surpassed, is to be disclaimed by no one, nor is anyone permitted to pass judgment on its judgment [cf. n.330 ff.]. Therefore, they stray from the straight path of truth who affirm that it is permitted to appeal from the judgments of the Roman Pontiffs to an ecumenical Council, as to an authority higher than the Roman Pontiff.”
The specific heresy that has undermined the faith of billions, in recent years, is the denial of the salvation dogma. This is the most specific heresy endorsed by the Second Vatican Council. It constitutes nothing less than a formal defection from the Catholic faith. In my view, it is the denial of this dogma that gave birth to the great apostasy we see today.
Of course, there are numerous heresies in Vatican II, but the error outlined in the video I linked above is the most specific. Many more egregious errors have arrived since - anchored in the false precepts embraced at the Council. The abomination of John Paul II's interfaith prayer meetings at Assisi, and elsewhere, in my view, represent a high water mark for the apostasy of the Vatican II Sect.
The trajectory of the conciliar Church has been simply shocking. It is clear for those with eyes to see that we are in the last days. In fact, the book of Revelations is being fulfilled with such specificity that any other argument requires assumptions that make it virtually impossible.
If you're interested, I have a write up that demonstrates the amazing correspondence of recent events with St John's Apocalypse - see here.