Duel between Arthur and Derian

The duel between Arthur and Derian occurred when Arthur Pendragon invoked the right to Queen Annis for single combat. Arthur was the champion for Camelot and Derian was the champion for Caerleon. Post-duel, Morgana enchanted Arthur's sword to make it several times as heavy, this plan was set to weaken Arthur, so Derían could easily defeat him. When the duel started, Arthur began fighting comfortably, but as time went on, it was getting heavy. Fortunately, Merlin supported Arthur with his magic, enabling Arthur to defeat his mighty opponent, form a truce between the kingdoms and bring peace to Camelot (His Father's Son).

Victory: Arthur Pendragon

Trivia

 * This duel has many similarities with the duel from the Old Testament story of David and Goliath.