On the subject of the various opinions of theologians (Bellarmine, Suarez, etc) on the "Pope heretic" question: these theologians treated of the question of "The Pope as a private theologian", not in his office as the Pope; Msgr. Lefebvre in his sermon of the 8th of November, 1979, summarizes the study of Dr.
Xaverio de Silverirahttps://www.sspxasia.com/Docuмents/Archbishop-Lefebvre/Apologia/Vol_two/Chapter_40.htm
The very objective study of Xaverio de Silverira on this subject demonstrates that a good number of theologians teach that the Pope can be heretical as a private doctor or theologian but not as a teacher of the Universal Church. One must then examine in what measure Pope Paul VI willed to engage in infallibility in the diverse cases where he signed texts close to heresy if not formally heretical.
Msgr. Lefebvre goes from affirming that the Pope can be heretical as "a private doctor or theologian", to treating of "to what extent Pope Paul VI willed to engage his infallibility....". But this is a jump from one subject to another; in other words, when Paul VI signed the docuмents of Vatican II, the N.O.M. etc., he was not acting as "a private doctor or theologian", but as "the Pope"; the same for his successors and their official various acts. None of the above theologians A.F.A.I.K. Have ever treated of a Pope in his official acts being able to teach heresy or enact measures that would lead souls to error, sin and perdition; this would be contrary to the very institution and purpose for which Christ founded His Church.