I recall from memory a story about an ancient Greek military leader that saved Athens (either from the Spartans or Persia or some other rival... I can't recall which) through the course of a war or battle. Immediately after the war was over, he was hailed as a hero, but over time the Athenian people grew to hate him for some reason, he lost a gov't election and was possibly executed by the people.
Does this story ring a bell? Can you direct me to the Greek story that I might be close to describing? My google fu has failed to uncover what I am looking for.
I believe you are thinking of Themistocles, who commanded the Greek navy at Artemisium and Salamis during the second Persian invasion and rose to be one of the most prominent politicians. He was ostracized (exiled) from Athens in 472 or 471 BCE, and was later framed by the Spartans.
He died in exile, though his reputation was later rehabilitated.
This is the story of Themistokles son of Neokles.
When the Athenians struck a large vein of silver in the silver mines at Laurion in 483 BC, Themistokles was the one who persuaded them to invest the money in their navy. When the Persians invaded 3 years later, he commanded that navy in battle against the Persian fleet. He suggested the plan that led to the Greek victory at Salamis in 480 BC. For this, he was honoured by the Athenians and others as the saviour of Greece. Even the Spartans, who were formally in command at Salamis, gave Themistokles royal honours in gratitude for his leadership.
He soon lost the respect of the Spartans, however, when he tricked them into standing idly by as the Athenians rebuilt their city walls. These walls had been torn down by the Persians, and the Spartans had ordered the Athenians not to rebuild them, which would have facilitated Spartan domination. When they discovered that Themistokles had pulled the wool over their eyes, they were furious, and began looking for ways to discredit the war hero.
Soon after the war, Themistokles lost the favour of the Athenian people. It's not entirely clear why this happened; our sources tell us that he became arrogant, perhaps even narcissistic, and thereby squandered the good will of the Athenians. He was sent into exile and went to live in Argos. At this point, the Spartans seized their chance, and accused Themistokles of being involved in a corruption scandal that had already led to the disgrace and death of the Spartan regent Pausanias. Simply put, Themistokles was accused of taking bribes from the king of Persia in a plot to bring mainland Greece under Persian control. Ancient authors agree that the accusation was spurious, but Themistokles fled Argos fearing for his life, and his flight was interpreted as an admission of guilt. In his absence, the Athenians sentenced him to death for treason.
After a series of narrow escapes from Greek communities in Western Greece and the Aegean, Themistokles finally fled to the court of the Persian king. There, he offered his services in return for royal protection. King Artaxerxes recognised an asset when he saw one, and gave Themistokles dominion over some cities in Asia Minor. He died there in 459 BC.
Sorry to latch onto this, but would Alcibiades not also fit the description by op? Perhaps someone with more knowledge can chime in?