From Hero to Demon lord

What would you do if you were summoned to a fantasy world as hero? To be the Hope of people? Your mission to defeat the evil demon lord?
Would you do it?
Austin Clarkson, a man from the normal world is summoned to a fantasy world and is told he could only be returned to his world if he killed the demon lord. After a decade of hardships he manages to kill the demon lord only to discover that their is no way back home. So what would be the best choice in such a situation, of course become the demon lord yourself and cause chaos yourself.
P.S: The MC is overpowered from the beginning. He will only grow stronger from there. Also there will be a harem but I won't be focusing to much on it.
Also cover picture not mine. if it belongs to you and want it removed please contact me.