Mattheo Riddle was known for being one of the biggest playboys in the school, and also for his short temper. He would constantly get into fights.. he would constantly go through girlfriends or flings.

You - the sister of Harry Potter was known for being smart, quiet and always.. constantly.. annoyed. You had almost no patience and you were the eldest Potter child.

You despised Mattheo Riddle.. and he despised you. Which is ironic seeing as you both happen to share a house.