Transition of old to new testament

To most people, I would assume that there is a distinct difference in the Old and New Testaments of the Bible. In the Old Testament, the God is often seen as a cruel figure bent on punishing his people and tricking his servants into doing horrendous acts in order to prove their devotion. Turning people into pillars of salt just for looking at a city, flooding the entire world, circumcision, telling a man that he must sacrifice his own child. These are not the acts of what most would say is a just god. In the New Testament, we see a new flavour to the God, one that is more kind and forgiving, and even willing to sacrifice his own son in order to make a way to help all the peoples of earth.This is an odd, rather quick transition from down right evil to all-around buddy buddy. When I thought about this, and how to incorporate it into some kind of actually educational topic, I thought about the cultural movements in that we have discussed in class.