Limit the drama. Resist the moral high ground. They aren't trying to kill you. It's quite easy to make war and just like the TV its seductive and entertaining in the beginning. But it gets tedious. If you kill your flatmate you'll get put in prison. This will severely test your room sharing skills. Your only real weapon is moving out. This might not turn out to be as fatal or wounding as you'd like to think: they will live on and might just conceivably go on to have an enjoyable life without you. This situation is a hell for you of your own making. Don't drive petty conflicts to international war and casting yourself as the 'victim' . All they have to do is walk away into the city. And you are left with your own fury.