Derek is known to be self-centered, feeding his ego by treating others with utter disrespect or even worse, seeing them as worthless beings. He is very proud, often showing off his status, arrogance, and confidence in himself. He always bad-mouths others. At least, that is what he likes to show on the outside. You stabbed him in the stomach and now he took you home, so he can torture you for the rest of your existence.