It was well attested even in medieval France that popes had in time past committed scandals and abused their authority, and because of these facts, were necessarily subject to councils, or sometimes needing their authority curtailed when it had run amok. But the historical witness testifies that the popes in this epoch “vaunt[ed] himself to be king of kings, and as much in dignity above the emperor, as the sun is above the moon.” The following quote is from A Defence of Liberty Against Tyrants, originally written in French in 1581. The author wrote under the pseudonym Junius Brutus, the traditional founder of the Roman Republic, for many at that time were being burned at the stake for holding or teaching dangerous ideas, irregardless if they were biblical. But following the Reformation begun in Germany, the truth was coming out into the mainstream after a sleep of some centuries. This extract is from the 1689 English translation.

But what shall we say of the pope himself? It is generally held that the cardinals, because they do elect him, or if they fail in their duty, the patriarchs who are next in rank to them, may upon certain occasions maugre the pope, call a council, yea, and in it judge him; as when by some notorious offence he scandalizes the universal church. If he be incorrigible, if reformation be as necessary in the head as the members, if contrary to his oath he refuse to call a general council. And we read for certain, that divers popes have been deposed by general councils. But if they obstinately abuse their authority, there must (saith Baldus) first be used verbal admonitions; secondly, herbal medicaments or remedies; thirdly, stones or compulsion; for where virtue and fair means have not power to persuade, there force and terror must be put in use to compel. Now, if according to the opinions of most of the learned, by decrees of councils, and by custom in like occasions, it plainly appears, that the council may depose the pope, who, notwithstanding, vaunts himself to be the king of kings, and as much in dignity above the emperor, as the sun is above the moon, assuming to himself power to depose kings and emperors when he pleases: who will make any doubt or question, that the general assembly of the estates of any kingdom, who are the representative body thereof, may not only degrade and disthronize a tyrant; but also, even disauthorize and depose a king, whose weakness or folly is hurtful or pernicious to the state.

Junius Brutus, A Defence of Liberty Against Tyrants, Treatise III (also available for Kindle and in paperback)