I mean, technically he is just a lich… Who so happens to have a cult that worships him, which somehow gave his incorporeal spirit power during his short absence after the defeat at the hands of his right-hand lieutenant, Kas, and has absorbed the power of a lesser deity to use as his own while escaping from imprisonment by the Lady of Pain for a failed plot to usurp the cosmic order when he infiltrated Sigil, the City of Doors.

So, not a god, just a lich with the power of a God.

Haha petty semantics!

“shouldn’t be too hard”?!

A regular lich is CR 21.

For comparison, an adult red dragon is CR 17 and the most powerful demon, the balor, is CR 19.

There are almost no creatures more powerful than liches. Even ones that are not Vecna.