Give him a cruel mercy
From Create Your Own Story
You allow your brother to leave humiliated at his defeat.
You continue your rule, confident that your brother will never return. His injuries are too severe.
Seven years later, your brother does indeed return. It turns out his injures were not as permanent you thought they would be and he is stronger than ever.
You end up fighting him again. This time he kills you.
You are dead.
I guess your should have killed him when you had the chance.