How can we better get rid of leaders that harm its citizens in very profound ways?

We have repeatedly seen how one leader/ruler of a country can literally enslave its people or commit it to wars far beyond what is rational. We let situations erode to a point where only war and bombing is necessary in order to oust that person. With all the advanced thinking that we are suppose to be able to enlist, I can not understand why we can not come up with a better way of replacing these leaders.

Our advances in technology are only enabling bad leaders to do more destruction. For all you great thinkers out there, I trust that one day you can feel good about the great things to create and develop. We are all minimized and disgraced by people that abuse those very same things.