The primary thing that all violent countries have is religion. Eliminate religion from the world and violent crime would bottom out. Or start with the two most violent of the worlds religions.
Islamic faiths of the Middle East and Christian faiths of the west. Christianity is an outdated superstition with no relevance for living today. Both Christianity and Muslim worship the same God, yet are mortal enemies due to stupidity. Remove the violent nature from both Christian and Muslim and you have the Jewish belief. Unfortunately, due to the ignorance of most people, no matter what faith they were born into and the built in survival instinct we all have (SUPERSTITION), we are raised to hate and fear each other. SAD.