David Cain - Batman: Wayne Family Adventures

Considered one of the world's finest assassins, David Cain was a skilled fighter, training Bruce Wayne during his global travels; Wayne would use his teachings to become the vigilante, Batman. 

Years later he fathered his daughter Cassandra Cain, raising her to become a living weapon. Refusing to teach her how to speak, he instead taught her how to read an opponent's body language, making her a near-perfect, lethal combatant. 

Despite her hesitation, David would push her to kill opponents, scolding her for any displays of kindness or mercy. 

This harsh training would eventually alienate her, leading to Cassandra leaving his care and joining the Bat Family as - originally Batgirl, then Black Bat - Orphan.