Louis II of Hungary
Despite their blood relation, Bona sometimes was a fierce opponent of the Habsburgs. She advocated attaching Silesia to the Polish Crown in return for her hereditary principalities of Bari and Rossano, but Sigismund the Old didn't fully support this idea. Wanting to secure her eldest daughter in the Kingdom of Hungary, Bona successfully supported her son-in-law John Zápolya as successor against Ferdinand of Habsburg after Louis II of Hungary was killed at Mohács in 1526.