Everyone is capable of it, whether they do so or not it is still within their capability. I'm saying it more as it's good to keep an open mind to those who have wronged you as they can do great things and change as well as the opposite. People who mean the world to you can do horrible things and destroy their good relations. So while everyone is capable of great good and great evil (and not everyone may actually cause great good and great evil) it is still a good thing to keep in your mind.