You know, I don't really understand why Luna is always portrayed as misunderstood and sympathetic in fanon regarding her transformation into Nightmare Moon.
Because of how her canon showed her regretting such an action and the fandom's hard on for Luna will not allow her being portrayed in any other way. I'd like to see a fanon art or story showing her having no such turn for the better. It would break that whole usual fanon idea of Luna.