What modern day wrong can be compared to Macbeth's desire to become King at all costs?

Well, look at Idi Amin Dada, the former president of Uganda. He killed everyone and anyone who didn't agree with his policies. (The movie The Last King of Scotland is about him). Look at what happened in Rwanda. Look at Haiti. The leaders of those countries were too self-absorbed, greedy and stupid to pay attention to what was happening in their own countries. Saddam Hussein, Osama bin Laden, heck, practically every leader in the Middle East is guilty of the same type of warped ambition. They do not care about the cost of their success (financial or human) only about power.