I am a Swedish guy living in Colombia, a country that is living a very similar situation to the one you described about Nigeria. It is an incredibly rich country but most of the population doesn't enjoy the riches of the land because of years of corruption, war, hatred and more.
I am more a believer of God than karma but I totally agree that it is time to break the circle of evil. Learn to forgive those that we think don't deserve forgiveness and love those who have hurt us. Or else it will never stop.
RE: Why does evil thrive in our present world?