The X-Men have a wide array of great villains, including many "big bads" like Apocalypse, Mr. Sinister, and Magneto. But beyond Mystique, there aren't very many female solo baddies even remotely close to their level. So which B-List X-Villainess would you want to see given more storylines to elevate their status as an X-Man villain?
NOTE: I left out characters more associated with other Marvel characters (Viper), reformed villains (Emma Frost, Frenzy), or characters most associated with teams (Vertigo, Phantazia, Dragoness, etc.).