Miracle Doctor, Abandoned Daughter: The Sly Emperor’s Wild Beast-Tamer Empress - Chapter 549

These days, could one really time-travel just by dreaming? And to become a silly princess at that. Well, marrying a domineering man wasn't too bad. His taking a concubine wasn't the end of the world either. But why was she forbidden from liking anything except him? That was just too domineering! She had to escape! Ah, but upon escaping, she realized he was a half-demon who didn't understand love... and, moreover, a half-demon who had a three-lives connection with her...

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

5 years after the world changed, the final boss appeared.