Human is neither completely good nor completely evil by nature. Human is born with both good and evil.
There is a fight between good and bad inside everybody. Human can choose on side or can be directed to one side and then one outweighs the other. There are reasons behind why one is superior than the other. Human lives in a society and is open to be affected by environmental factors. Good and evil inside human is grown by what is given to him or by what he experienced. Education plays a very big role here. Education in family is very important. Good must be taught during the childhood. Religion and ethics also have an important role. Both of them try to lead human to the good. On the other hand, human is born with certain characteristics. Emotions like envy, arrogance, selfishness can be stronger in some people by birth than the others. All these above-mentioned factors can determine which way you will most likely to choose.
Nowadays people are living in very hard conditions in most part of the world. Such as economic crisis, wars, unemployment, poverty, discrimination. Under these circumstances people can be prone to be more angry, self-centered, intolerant, disrespectful which are some signs of evil. Moreover, people can do things which are not morally or legally right. These are mostly caused by the external conditions which people are subject to.
To sum up human has potential to do both good and bad. I believe under peaceful world good would definitely outweigh the evil.