This conversation definitely freaked me out. Emma never hurt anyone more than emotionally as the Dark One. She still had a very good grasp on the light within her, but Killian gave into the darkness almost immediately. He became very violent, unafraid to hurt anyone or stop them from getting in his way. After all, he sentenced all of Emma's dearest friends and family to the underworld. As the Dark One, he was all revenge and torture. His methods were physical while Emma manipulated emotions.