i guess the question is, "when does a leader become a tyrant?" or "what makes a leader be a tyrant.
for me the problem is that my definition of a leader, is also a part of my definition of a tyrant.
"all tyrants are leaders, but not all leaders are tyrants."
but I agree that an actual tyrant is, as Doom said, a leader of a nation.
or at least a self-proclaimed leader of part of the land. tyrants do not really have to be recognized by other nations to get their rules be law.