Hades - Besides being inaccurate (which isn't necessarily an issue for me depending on the execution), it's also cliche and unimaginative.
Hecate - Same as Hades. The closest we got to this idea being good was James Tynion's Justice League Dark and even then it was just her "crone" aspect being evil.
Vanessa - It worked for one story that was a meta commentary on how DC treated her and that's it.
Hera - See Hades and Hecate's entries.
Max Lord - Similar problem as Vanessa.
Medusa - Great as Rucka's run was, I'd drop Medusa being used as a villain if I could.
As a bonus, here are characters that are already villains but could work as heroic or neutral figures in the hands of really good writers:
Ares - Been done before by Perez, Rucka (twice) and Azzarello.
Circe - Was attempted by Messner-Loebs with.... mixed results. Could be done if Circe were examined through a feminist lens like the Amazons.
Angle Man - He's simply a thief and can be good or antagonistic without going fully heroic or fully villainous.
And characters who absolutely should be villains:
Zeus - Represents everything Diana hates far better than Ares.
Poseidon - As much of an asshole as his brother.