I tend to take the view that most people, without mental disorders or other decision impairing effects (Those two variables wouldnt stop you from having a good or bad soul, only make it far harder to understand if you were acting out of mania or making a conscious choice) are largely influenced by their environment and act accordingly. I like to think that, at the beginning, you come into this world pure, neutral - no grasp of good or evil.
As time goes on, and you mature, what you look like, who you are, who you know, where your born - a thousand thousand variables - all shape your conscious and unconscious mind. Every little thing thats ever happened to you, every tiny coincidence - that time you missed the bus, when you came second in the school 100 metre race, when you bullied someone weaker than you out of frustration...I couldnt even begin to cover the magnitude of things that influence you in a mere forum post.
People are largely going to become what they are pushed into being by the circumstance of life. I say largely, as I have long believed that you do NOT have to be a victim of negative circumstance. People sometimes do have very little chance to escape a negative, downward spiral - its heartbreaking to watch. I had many disadvantages growing up, and this has left its mark on my soul - but not so many as the child with no food in some barren country. I counted my blessings, a loving family who all gave me so much (sometimes unrequited) love and help. I always liked to believe I was a self made man - that I rescued myself from my background and pushed myself onward, but the truth is that my success is mostly circumstance. The help of my family? circumstance. My will to make the best of my life? again circumstance - based on the events of my life. I could so easily have been sucked in. I still slip occasionally.
My simple answer? I tend to believe that most of humanity doesnt stray far from neutral - they live their lives and do a variety of both good and bad deeds.
Others choose what could be (and this is never black and white) More extreme paths. There are those messianic people who take the pain of others and reduce it. There are those who choose to be a negative force in the world. This is not a simple area, and raises so many questions. Are we simply victims of our past evolution? do good and evil matter in terms of species survival and evolution, or are these just self-deluding ideals that some of us lean on? The sheer scope of this question is making me somewhat dizzy as I type this.
I have my suspicions however, that people are fundamentally people. Theres a heartbreaking amount of apathy, hatred and evil. But at the same time, there is so much warmth, love and goodness in us. I think fundamental, pure good or pure evil exist so rarely as to be almost unseen. Most people are, as I said, simply people - we have equally capacity as both saint and sinner.
I think the most sensible, considered answer is, as always to simply say that it is "All a matter of perspective" And at the risk of sounding somewhat pretentious, I will leave you with a quote that comes to mind -
"If we could read the secret history of our enemies, we should find in each man's life sorrow and suffering enough to disarm all hostility."
Its this that reminds me that a murderer in the news isnt the product of himself. And that a saintly girl who seems to be the best of us, might not have been, once.