For example, see:
Again, I will reaffirm that in its 2000 year history, there have been popes that were less than model christians. The Church is Christ's bride (Ephesians 5:29) and has "no spot, wrinkle or blemish" (Ephesians 5:27). Christ also stated that the gates of Hell will not prevail against His Church (Matthew 16:18) so how can the Church commit error? Individual clergy may commit sins, even popes commit sins because in the Church there are both "weeds and wheat" (Matthew 13:30).
In so far as the priest is a public officer of a holy Church, a blameless life is expected from him, both because he is by his office the model of virtue to whom the laity look up, and because his life, when virtuous, inspires in onlookers respect for the society of which he is an ornament. But the treasures of the Church, her Divine character, her holiness, Divine revelation, the grace of God, spiritual authority, it is well known, are not dependent on the moral character of the agents and officers of the Church. The foremost of her priests cannot diminish by an iota the intrinsic value of the spiritual treasures confided to him." There have been at all times wicked men in the ecclesiastical ranks. Our Lord foretold, as one of its severest trials, the presence in His Church not only of false brethren, but of rulers who would offend, by various forms of selfishness, both the children of the household and "those who are without". Similarly, He compared His beloved spouse, the Church, to a threshing floor, on which fall both chaff and grain until the time of separation.
This is borne out by the fact that within its 2000 year history, not one pope has ever erred in proclaiming doctrines of faith or morals. This is yet one more affirmation of the role of the Holy Spirit in the Church.
Now that you have researched the "worst" popes, do yourself a favor and read a list of the "best" popes. In our lifetime, we have been truly blessed with John Paul II and now, Benedict XVI.