Lady Jessica and her shoulda-been un-campy serial murders of the Dallas cartel. (I say a STRAIT-JACKET-style slew of axe murders all Season 13 (dvd) would do nicely).
After killing nearly all of the cartel (instead of Clayton's business partners we didn't know) whom she'd been blackmailing for 40 years over Dusty's paternity issues, only Marilee Stone survives -- but pouty Marilee uses her minimal injuries to obtain special favors from the Ewings (mostly from JR, because Bobby still won't play ball). And that's even scarier than Lady Jessica!