Onyx and Lea
Onyx was the very first nephlem leader. With his companion/daughter by his side, he ruled the knights with an iron fist. Even though they were tired of the fight with the dragons, Onyx would not lighten up on them, not even in the slightest. And as a result, the knights were stronger than they had ever been.
Lea is the offspring of Onyx and her late dragon mother. Onyx defiled the dragoness, and in turn, gave birth to his daughter. Not very long after, Onyx slew the dragoness, taking his daughter with him as to train her to be one of his loyal subordinates.
In time, she out-shined him and even took his spot as leader when he died. She was the one the slew the last dragon.