“Villain” is such a broad category, isn’t it. I mean, it could mean anything from a dominating empress seeking to conquer the world, to just say, a professional thief, trying to get her next big score. 
The lower the ambition of a villain, the more practiced and relaxed of a relationship they seem to have with their hero. The dynamic being more of a friendly rivalry that a battle between two nemeses. This relationship also often seems to have quite a bit of sexual tension, maybe spoken, maybe left unspoken. In extreme circumstances, this *villain* might, if push comes to shove, abandon her precious treasure to even help the hero, and at that point well she kind of loses her villain card, doesn’t she? And I just think that makes her fair play.
Maybe this thief gets a tip on a new precious amulet being moved into a museum, one worth quite a bit of money, unaware that a real villainess like you gave her this tip without all the information. Leaving the poor lady thief, unaware that this amulet is a cursed with runes invoking lust, fertility, subservience, and is tied directly to your power. After disabling some security, camera cameras, sexily moving through laser grids in her skin suit, she perfectly steals, the amulet, replacing it with a fake, all for no one to notice, whispering to herself, just how good she is at this.
Of course, on a rooftop later that night she took the amulet out of her back, stared at it for a little bit, became a enamored with it, maybe putting it on wouldn’t hurt… right? 
I’m glad to have an Ask that acknowledges the importance of the varieties of villainy<33 and of course the spectrum along it which we all fall upon. We can’t have anyone slipping too far away now! It’s such an awful thing when an aspiring young Villainess looses herself to a pitiful ‘redemption arc’ so often brought on by a meagre hero~
I’m not manipulating them really, I’m just doing them a favour and pushing them back up the scale towards where they should be! Away from their silly nemesis trying to convince them to do the wrong thing and back towards true villainy~ Back towards me<3 There’s nothing wrong with sexual tension with your nemesis of course I just need to make sure that the inevitable seduction results in an extra villain rather than hero~
All of this is to say I’m sure our Lady thief will love her new amulet that I left her! I almost don’t know why I bothered with the defences but couldn’t have her catching on could we~ The poor darling never stood a chance once she held the amulet though of course<3 I’d inscribed enough runes to draw in any soul who felt it in their finger tips~
All that desire pent up in her, chasing fortune and thrill seeking heists she was always going to be perfect prey to my powers~ The second she slipped it on that desire for wealth would be desire for me<3 and it’s far mote potent too~ Drowning in her own lust and fertility grinding and moaning there on the rooftop the second the pendant was round her neck~ Moaning my name in subservience as if she’d known it her whole life~
For now she’s been temporarily reshaped into my own personal treasure, doting on me and following around offering her pussy constantly in wild desperation~ A fair punishment for falling towards the light<3 after a while though I’ll help her become a true villain again~ No doubt her old nemesis will come looking eventually; it’ll be so satisfying to have her break them mercilessly fully bent back to the dark via her lust for me<33