Please answer the following question: Given the following context:  Alexander perhaps undercut his own rule by demonstrating signs of megalomania. While utilizing effective propaganda such as the cutting of the Gordian Knot, he also attempted to portray himself as a living god and son of Zeus following his visit to the oracle at Siwah in the Libyan Desert (in modern-day Egypt) in 331 BC. His attempt in 327 BC to have his men prostrate before him in Bactra in an act of proskynesis borrowed from the Persian kings was rejected as religious blasphemy by his Macedonian and Greek subjects after his court historian Callisthenes refused to perform this ritual. When Alexander had Parmenion murdered at Ecbatana (near modern Hamadan, Iran) in 330 BC, this was "symptomatic of the growing gulf between the king's interests and those of his country and people", according to Errington. His murder of Cleitus the Black in 328 BC is described as "vengeful and reckless" by Dawn L. Gilley and Ian Worthington. Continuing the polygamous habits of his father, Alexander encouraged his men to marry native women in Asia, leading by example when he wed Roxana, a Sogdian princess of Bactria. He then married Stateira II, eldest daughter of Darius III, and Parysatis II, youngest daughter of Artaxerxes III, at the Susa weddings in 324 BC.Meanwhile, in Greece, the Spartan king Agis III attempted to lead a rebellion of the Greeks against Macedonia. He was defeated in 331 BC at the Battle of Megalopolis by Antipater, who was serving as regent of Macedonia and deputy hegemon of the League of Corinth in Alexander's stead. Before Antipater embarked on his campaign in the Peloponnese, Memnon, the governor of Thrace, was dissuaded from rebellion by use of diplomacy. Antipater deferred the punishment of Sparta to the League of Corinth headed by Alexander, who ultimately pardoned the Spartans on the condition that they submit fifty nobles as hostages. Antipater's hegemony was somewhat unpopular in Greece due to his practice (perhaps by order of Alexander) of exiling malcontents and garrisoning cities with Macedonian...  answer the following question:  Who was defeated at the Battle of Megalopolis?
A:
Agis III