As the Demon King, I Am Very Distressed Because the Hero Is Too Weak 1.0

I am the Demon King Sarthis. If I go according to the script, I, the Demon King should be defeated by the Hero on the destined night every five hundred years. After that, I can gloriously leave the field and live as a lazybones. I’ve been working diligently for this purpose for hundreds of years, and finally, I met my fated opponent. As a result, this guy is so weak he couldn’t even pierce through the first layer of my armor with his ultimate move. ……What methods could I use to lose to this Hero? Urgent, waiting online!