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Antipope John XXIII, born Baldassare Cossa, succeeded the controversial Antipope Alexander V upon his death in 1410. Despite pledging allegiance to the Council of Pisa that aimed to end the Western Schism, John XXIII wavered, seeking personal gain. His actions drew criticism from reform-minded individuals, including Jan Hus, who condemned ecclesiastical corruption and called for reforms within the Church, eventually leading to Hus's persecution and eventual execution.