What are some specific governments which either rose to power interestingly, became corrupt, or failed?

I have been assigned to write an allegory for a specific type of government, much like the story Animal Farm. Animal Farm deals with Russian communism, so I don't want to write about that, or communism in general.



I will research any ideas answerers give me, and any government system is acceptable.



Thanks in advance! And please let me know if I should add any information.
What are some specific governments which either rose to power interestingly, became corrupt, or failed?
One only needs to turn to Rome,and the Roman Empire to see what a great idea was and how corruption of absolute power destroyed it.