The Bad Popes is a 1969 book by E. R. Chamberlin that documents the lives of eight of the most controversial popes (papal years in parentheses):

Pope Stephen VI (896–897), who had his predecessor Pope Formosus exhumed, tried, de-fingered, briefly reburied, and thrown in the Tiber.^[1]^: 19
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.^[1]^: 153
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.^[1]^: 204
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.^[1]^: 218
Pope Clement VII (1523–1534), also a Medici, whose power-politicking with France, Spain, and Germany got Rome sacked.

References