Pope Stephen VI (896–897), who had his predecessor Pope Formosus exhumed, tried, de-fingered, briefly reburied, and thrown in the Tiber.[1]
Pope John XII (955–964), who gave land to a mistress, murdered several people, and was killed by a man who caught him in bed with his wife.
Pope Benedict IX (1032–1044, 1045, 1047–1048), who "sold" the Papacy
Pope Boniface VIII (1294–1303), who is lampooned in Dante's Divine Comedy
Pope Urban VI (1378–1389), who complained that he did not hear enough screaming when Cardinals who had conspired against him were tortured.[2]
Pope Alexander VI (1492–1503), a Borgia, who was guilty of nepotism and whose unattended corpse swelled until it could barely fit in a coffin.[3]
Pope Leo X (1513–1521), a spendthrift member of the Medici family who once spent 1/7 of his predecessors' reserves on a single ceremony[4]
Pope Clement VII (1523–1534), also a Medici, whose power-politicking with France, Spain, and Germany got Rome sacked.
In my spare time I looked up your information source...a book by E.R.Chamberlin with a 3.7 rating and available many places on the internet for $1.00 (Kindle version for $.99)
I could locate no information at all on the author to see what his qualifications were. The Popes described were in officw for a total of 71 years and 134 days. The office of the Pope has existed for 2,015 years and 30 days so their average isn't that bad.....71/2015 isn't a real large fraction.
The main problem with the ones who caused the most concern was that they were hand in hand with crooked political figures of their time....their moral failures were just that...men being evil men.
It is aan interesting insight however and I'll read a little more about them
Another fraction of interest is 8/266....that's bad Popes over all Popes, another miniscule fraction....not good of course, but I'd bet that the fraction of bad presidents/all presidents would be worse and this country is only a little over 200 years old.