And I'll explain my reasoning:

9 circles of hell.

7 rings of hell

1 sin per ring: Pride, Wrath, Gluttony, Greed, Lust, Envy, Sloth

I suspect that the other two circles were either collapsed rings or rings that were locked away for being too strong, and those two rings are the Ring of Glory and the Ring of Corruption. How Corrupt was made (most of you know this) is he once was human who was taken in for experiments to become the virus that overtakes hell.

The ring of Corruption had this virus.

So the proffessor (who happens to be an Austrian painter) sends some of the imps and other hellborns to break the barrier into the Ring of Glory, a frosty wasteland, and travel across it to get into the Ring of Corruption and collect a small smaple of the goo that resonated on the buildings and streets.

The plan backfired, however, unleashing both of the demons of those rings: Ulmoth, the embodiment of Corruption, and Evelon, the embodiment of Glory.

How is Corrupt the deadly sin of Corruption if Ulmoth is already the embodiment of it? Simple: Corrupt's body is a prison for Ulmoth, same goes for Frostbite and Evelon. Think of it as the Ink Demon and Bendy in Bendy and the Dark Revival. Same body, different appearances and personalities.