My candidate is a knight from my country:
Zawisza Czarny z Garbowa (Zawisza the Black of Garbów, also known as The Black Knight), was a Polish knight and nobleman. He served as a soldier and diplomat under the Polish king Władysław II and Hungarian-Bohemian king Sigismund of Luxembourg. During his life, he was regarded as a model of knightly virtues and was renowned for winning multiple tournaments. His nickname is due to his black hair and his custom-made, black armor, which is kept at the Jasna Góra Monastery.
In 1410 he took part in the Battle of Grunwald against the Teutonic Order. After the battle he proposed a peace treaty between the King Jagiełło of Poland and King Sigismund of Luxembourg of Hungary, which came to be known as the Treaty of Lubowla. In 1412 he participated in the conference between Sigismund, Wladyslaw II and Tvrtko II of Bosnia at Buda, where he won the tournament held there, with 1500 knights present.
Zawisza was a diplomat as often as a warrior, being many times an envoy for the Polish king Władysław II and Hungarian-Bohemian king Sigismund of Luxembourg. As one of six diplomats that represented the Polish Kingdom and king Władysław Jagiełło at the Council of Constance, where he was one a very few supporters of the church reformer Jan Hus and consequently strongly opposed his condemnation and subsequent execution.
In 1416 he participated in a tournament in Perpignan in which he defeated the well-known knight John of Aragon.
Zawisza participated in the Hussite Wars on the side of king Sigismund.
In 1428, Zawisza, with his retinue as a commander of light horse banner of 500 horsemen, joined the forces of Sigismund in the king's war against the Ottoman Turks. During that disastrous campaign he fought the Turks at the Battle of Golubac on the Danube in modern-day Serbia. Sigismund army was defeated by the Turkish forces. They had to retreat across the Danube, with only a few boats to ferry the troops over to safety. Zawisza's banner was guarding the retreating army. Being a man of importance, he was personally sent for by king Sigismund. He allegedly refused to retreat, disheartened by king's apparent cowardice. He was either killed in combat or executed in Turkish captivity.