Responses
Its because he was envious of her, she is talented and smart. He was always compared to her so he hated her for it and he somehow blame her for jeremia (tia's mom) death since Jeremia is very important to him. All in all its because of his envy and resentment that led him to hurt and execute her in their past life.
I am so confused why did the Prince hate tia in her past life?!? What could tia possibly have done to the prince to make him hate her?!?!?! At this point I don't even care about spoilers#－.－)