His tyranny caused the Aleuadae of Larissa to invoke the aid of Alexander II of Macedon, whose intervention was successful, but after his withdrawal Alexander treated his subjects as cruelly as before. The Thessalians now applied to Thebes; Pelopidas, who was sent to their assistance, was treacherously seized and thrown into prison (368), and it was necessary to send Epaminondas with a large army to secure his release. Alexander's conduct caused renewed intervention; in 364 he was defeated at Cynoscephalae by the Thebans, although the victory was dearly bought by the loss of Pelopidas, who fell in the battle.
Alexander was at last crushed by the Thebans, compelled to acknowledge the freedom of the Thessalian cities and to limit his rule to Pherae, and forced to join the Boeotian league. He was murdered by his wife's brother at her instigation. Ancient accounts agree in describing Alexander as a typically cruel and suspicious tyrant.
Initial text from 1911 encyclopedia -- Please update as needed