What is the most difficult thing for you to believe?

Everyone can be redeemed. I believe this, but it's definitely hard for me. I would like to believe that the world is a happy place filled with generally good people, but the reality is far from that.
People wound, kill, maim, mutilate, molest, rape, torture, and a thousand other horrible things. It's sad and violent and not fair.
And yet I try to maintain that everyone has the potential to grow and change, no matter what they have done.
It's definitely the most difficult belief I have. I rarely meet someone who agrees with me on the subject.
And it's actually the opposition's stance that makes it easier to believe this. People generally respond with anger and the need for violence on subjects such as murder or rape. And that makes me sad, and I realize that reacting to violence with violence can never save the world.