7. Madelyne Pryor
Madelyne Pryor was a clone of existing X-Men movie character Jean Grey. She was created by the evil Mister Sinister with the long-term plan of having her reproduce with Scott Summers (Cyclops) in order for him to manipulate the inevitably powerful child in to becoming a villain. She possessed the same powers as Jean Grey - telekinesis, telepathy etc - making her a huge threat to the X-Men when she became a villain. Later stories would see her become the Goblin Queen - influenced by the evil, magical demon S'ym - which saw her powers amplified by mystical means and also gave her various magical abilities of her own; including the ability to warp reality itself. Having a clone of Jean in the X-Men movie universe could potentially make for an emotional and intriguing storyline, while introducing Madelyne could also be a way to introduce magic to the franchise.