Power Girl (DC comics)
Trigon (DC comics) could also do a girl virson of him. Or a bieng from his realm.
Deviant (MCU)
Muscle girl/troll girl/ ogar girl. theres very few muscle girl mc's and many people like them (including me)
Bilble God/Jesus but a female version.
7 deadly sins(the real ones, not the meliodas kind) lust/gluttony/greed/sloth/wrath/envy/pride.
female voldemort.
female monkey king (mabe other genderbent deity's)
Terraxia/female thanos (earth-616 marvel) or just do a genderbent mcu thanos.
DXD 666
Sentinel (marvel comics) bieng reborn as a sentinel.
Proxima midnight (marvel comic/mcu)
Galvan (Ben 10)
Magic mirror (mirror mirror on the wall)
Flerken (cat from Captain marvel)
J.A.R.V.I.S. (mcu) could be a love intrest
Beelzebub ( could also have an isekai were mc born a fly, evolves to become beelzebub)
any guardians of the galaxy (for some reason i cant find a fanfic about it)