Also, for a Classical-age one, Thessaly, which OTL barely did anything for most of Ancient Greek history, had a brief period under Jason of Pherae where it suddenly looked as if they were going to step into the power vacuum left by the collapse of Spartan hegemony and become the dominant power in Greece. While Jason or a successor's turning around and matching the achievements of Greece's OTL Macedonian conquerors/unifiers from there seems far-fetched, Thessaly, rich and fertile, had the potential to create a lasting hegemony if a longer-lived Jason had managed to craft a succession plan (OTL after his assassination Thessaly just kinda fizzled).
The same goes for Thebes under Epaminondas, which, after Jason's assassination, actually did briefly construct a hegemony. The wank here is less about area controlled (for 9 years Thebes was the clear dominant power in Greece), and more about duration; OTL the Thebans won a great victory at Mantineia that would likely have solidified their dominance, if Epaminondas and the two man he wanted to succeed him had not all died there. Avert this, and it's possible a Greece united under Thebes is ready to face Philip of Macedon when he comes knocking, and, having repulsed this threat, might be ready to function as a great power for the long haul. A unified Greek Peninsula probably stands a strong chance of blossoming into a large empire in the long run, as Alexander's conquests demonstrate.
One other Ancient Greek one: Corinth. It had perhaps the best strategic placement of any Greek city, was a center of trade, an influential colonizer and a strong military power. But it never managed to assert its dominance over other cities in the way that Athens, Sparta, or later briefly Thebes managed to do, and remained a small city state that seemed to punch below its weight for much of its history. I see no reason why a Corinth that gets luckier with its leadership and political stability can't rise to lead, and eventually perhaps even rule, Greece.