Patience & Empathy (because you know the person must be hurting inside to be behaving in a toxic manner) initially, and if the person is completely unresponsive to your attempts to improve the interactions/exchanges - then you owe it to yourself to remove yourself from or avoid that type of environment as to not allow someone else to continually bring you down and negatively impact your own state of being. Some people just aren't ready to change their ways and you can't help them do that if they aren't receptive of help/feedback or ready and willing to make the necessary changes/improvements. You don't have to feel guilty for walking away when this happens either - they'll eventually 'get it' and then open themselves up to improving themselves.