It's the city-state of Sparta cause eventually they won the peloponnesian war, but in fact no city-state ever gained control of all Greece it was the Macedonian kingdom that finally controlled all of Greece years later
The Peloponnesian War was one of the most important conflicts of antiquity. This war took place in Greece between the Delian League (led by Athens) and the Peloponnesian League (led by Sparta). The war was very significant because it changed the balance of power in Greece. Athens lost all of its power, and was greatly reduced in importance. On the other hand, Sparta became the leading power of Greece, gaining control of the whole territory for a short period of time.
