In The Decline and Fall of the Roman Empire, Gibbons reports on the trial of Pope John XXIII in 1415, during which "the most scandalous charges were suppressed: The Vicar of Christ was accused only of piracy, murder, rape, sodomy and incest."
And he wasn't even the worst of them. Jesus, there have been some bad popes over the years. Even in modern times, we've had a few serious losers; Pius XII, by many accounts, was way too friendly with Adolf Hitler.
So it's pretty hard to call the current occupant of the Throne of St. Peter the worst pope ever; there's plenty of competition.
But folks, the former Cardinal Ratzinger is turning out to be so awful that he's going to go down in history as one of the all time horrible leaders of a crumbling Catholic Church. This guy was actively involved in covering up child abuse scandals. He knew what was going on, and he not only ignored it -- he ordered the bishops to report the crimes only to Rome, and not to civil authorities. He's guilty not only of protecting the worst kind of criminals -- authority figures who prey on children -- but of actively seeking to prevent them from facing the consequences of their crimes.
If Bill Clinton was charged with obstruction of justice for lying about a (consensual) blow job (involving two adults), then Pope Benedict XVI ought to be indicted in every country that has similar statutes, starting with the United States. All it takes is one district attorney, one grand jury. The evidence is pretty clear. Then Interpol can put out a warrant for his arrest.
Of course, all that would do is keep the guy holed up in his nice, big house in Rome; the Vatican is its own sovereign nation, with its own laws and rules -- and I don't think Canon Law provides for obstruction charges (or any charges) against the head of state.
See, that's the thing: Nobody can touch the pope (bad metaphor). There's no procedure for impeachment. He's the least accountable head of state in the world; even military juntas and dictators can be overthrown by force, but I don't see any revolutionary cadre of young Cardinals rising up and turning the Swiss guards on Il Papa. Too bad: A nice middle-ages-style coup in the Vatican might be just the thing to shake up that moribund institution and remind its leaders that the rest of the world will only take so much abuse.