Every story needs a villain that disobeys the rules. Bereft of drama we lose interest in the hero's tale.
Struggle makes us human. The will to defeat Goliath comes with an exaggerated sense of faith.
We overcompensate for our vulnerabilities, and in doing so, raise the stakes of our own determination. “He who has a why to live for can bear almost any how,” wrote Nietzsche in the Twilight of the Idols.
Very few fighters go undefeated. It's up to the hero to accept risk in the possibility of a loss. A creature of pure whim and incoherent self ultimately meets their maker.