An oligarchy is a small group of people controlling the interests of a much larger population. I know of no country governed that way in current circumstances unless you say it a government that is controlled by a cabinet. Then there are many countries that do that.
Tyranny is the last one. Usually one man at the top controls everything a country does. Tyrannies do tend to be cruel. It's the only way many of them can hold power.
Democracies tend to work from the bottom up, not the top down. A democracy is ruled by the population being governed.
