White Tiger

Angela del Toro, an FBI agent-turned-superhero, could easily serve as a femme fatale for the show's second season, especially if Marvel wants to keep Elektra on the backburner. It'd be great to introduce del Toro as an FBI agent investigating Daredevil's rise in Hell's Kitchen while interweaving her origin story with her hunt for Matt Murdock. Add a little bit of the martial arts history of the character (which could potentially tie nicely into Iron Fist) in there as well and you've got yourself one hell of a subplot.