Dahlia (The Originals)

Dahlia Mikaelson was Esther's older sister, a powerful witch and possibly the REAL true main antagonist of The Originals due to her dirty deal with Esther, promising her a fertility spell if she kills every first born of her generations and if she fails to do that, she will go after her and her whole family.

This is possibly why Hope was a "danger" to the witches in New Orleans and why Esther wanted to kill her, she was "trying to protect" her family from getting killed.

She could possibly appear in The Originals and become a major threat to the Mikaelsons and Hope and it will possibly cause an unlikely alliance between Klaus and Esther as Esther is afraid of Dahlia due to her being a much more powerful and dangerous witch then she is.

Dahlia was a cold, wicked, spiteful and manipulative woman who was also dangerous and never cared about the consequences. She is the Bigger Bad of the Originals.