Who has complete control over government?

This is a very vague question, and needs far more details. Although it varies from country to country, government is generally self-controlled. In other Words, parts of the government watch over other parts to make sure the power stays in place. Each branch of government controls a certain aspect of the government. In a Dictatorship, there is a single ruler, who has the last say in everything.

Conspiracy theorists have all sorts of beliefs, ranging from a single individual making decisions under a 'shadow government', all the way to aliens.