Dante doesn't have much time for popes. At least for those who transgress what he regards as the appropriate bounds of their authority. There are numerous pontiffs in Dante's vision of Hell, cast down for a multitude of sins, and Anastasius II is one of them.
He was pope in the late 5th century AD and during his pontificate tried to heal a schism or breach between rival factions in the Church. In doing so, he agreed to meet with Photinus of Thessalonica, who had been labelled as a heretic by Anastasius' predecessor as pope, Gelasius I. The very idea of granting an audience to a confirmed heretic was considered scandalous to many and Anastasius' reputation was seriously damaged as a result. He died shortly after his audience with Photinus, but his name lived on in infamy, and he became the first pope in history not to be made a saint. Dante's somewhat unfair treatment of Anastasius is further compounded by the fact that most scholars think he got the pope confused with the Byzantine Emperor, Anastasius I.