Most commonly historically rulers have united nations through conquering. Large areas of land can be the Roman empire which consisted of almost the entire Europe and North of Africa, then another can be Mongolians taking over China, Russia, and Asia, and the Third can be the Ottoman Empire that ruled over Asia, the middle east, and parts of Europe. The great leaders who managed to unite can be Alexander the Great, Napoleon, Queen Victoria. These three mostly got other countries by conquering them or colonizing them.
