Extreme nationalism, devotion to a single ruler, use of force and terror and censorship of information is called Socialism, Liberalism, Fascism or Ethnocentrism?

The best answer here is : Fascism.

Especially devotion to a single ruler is not a characteristics found in the other systems, as they're more focused on "the people" rather than on a strong ruler.

Socialism is an economical system based on a controlled market, liberalism calls for little control of the state and ethnocentrism is the focus on one's own ethnicity.