Government systems based largely on the personalities of one person are the most dangerous political systems that the world has produced. The genocidal monsters of history and strongmen that exist throughout Latin America, Asia, Middle East, and Africa have brought riches and prestige on themselves while bringing ruin and misery on everyone outside their inner circle. The greater damage may occur though after the dominant leader has passed away. Institutions in dictatorships and one party states are often weak or non existent, creating a power vacuum that is often filed by another strongman who is cunning enough to rise above the free for all.
One man rule is prone to the dreaded cult of personality, which never leads anywhere good. Many of these states are also heavy handed police states, with large police forces to crush any descent against the ruler they serve. The states themselves become very personalized around the thoughts and ideas of that one man, who in some cases demands to be approached with god like reverence. The advantages to such a system are largely exercises in self interests, while disadvantages can linger for decades following the rulers death through economic stagnation, lack of vital social services, and mistrust of government.