Grademon

Grademon is a general in Digimon Xros Wars. He resembles a golden knight, but when he's corrupted, he's purple

Digimon Xros Wars
Grademon first appeared as his corrupted self. Shoutmon X4 defeated him and reverted back to his good self. Grademon later saved Taiki from an attack from Tactimon and sacrificed himself to destroy Tactimon's tower.