Tyranny exists. All too many politicians want unlimited power, to be tyrants; it is why they go into politics. Joe Stalin was one of the nastier examples that proved it. Brown didn't quite make it but he did a huge amount of damage. You can probably think of others. Fred explains the reality of life in America under Obama. If that isn't tyranny, it will do until the real thing comes along.
Tyrant ex Wiki
A tyrant (Greek τύραννος, tyrannos), in its modern English usage, is an absolute ruler unrestrained by law or constitution, or one who has usurped legitimate sovereignty. A tyrant usually controls almost everything, and is considered a ruler of horrible and oppressive character. The original Greek term, however, merely meant an authoritarian sovereign without reference to character, bearing no pejorative connotation during the Archaic and early Classical periods. However, it was clearly a negative word to Plato, and on account of the decisive influence of philosophy on politics, its negative connotations only increased, continuing into the Hellenistic period.
Plato and Aristotle define a tyrant as "one who rules without law, looks to his own advantage rather than that of his subjects, and uses extreme and cruel tactics—against his own people as well as others". During the seventh and sixth centuries BC, tyranny was often looked upon as an intermediate stage between narrow oligarchy and more democratic forms of polity. However, in the late fifth and fourth centuries, a new kind of tyrant, the military dictator, arose, specifically in Sicily.