Yes.
In the original Forgotten Realms setting, the supplement "Old Empires" by Scott Bennie detailed the realms of Mulhorand, Unther, and Chessentea. Unther, in particular, was ruled by Gilgeam:
Enlil himself retired; he appointed his son, Gilgeam, as his successor as king of the gods. At first, Gilgeam was a just ruler. But sometimes even the gods can go mad.
Gilgeam was a proud god-king. As the centuries passed and Unther declined in prosperity and influence, as taxes rose and the peoples hatred grew, Gilgeam
became a cruel and jealous lord.
Gilgeam's alignment in stats blocks is given as Lawful Evil, but the text described above makes it clear that this was not always the case, unless one can reconcile "just ruler" with a lawful evil alignment.