MTL - Invincible Leveling King - Chapter 40 Killing the purple robes (below)

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

An ordinary office clerk was accidentally reborn into a vast and mysterious world of Xianxia, becoming a member of a small cultivation clan.The story begins in an endless sea of sand, in an oasis called the Yuquan Lake Oasis.

Mythical Abode Mountain, Cloud’s End Cliff, the most dangerous of Azure Cloud Continent’s four deadly areas. Cloud’s End Cliff’s base is known as the Grim Reaper’s Cemetery.

Kael, a reclusive and antisocial man, died alone in his apartment, consumed by frustration and regret. But his tale didn't end in darkness. Reborn in the unforgiving world of Eridoria, where the law of the jungle reigned supreme and apes were eerily absent, Kael found himself in the body of a lion cub with a unique bloodline.This was no ordinary rebirth; he was a lion unlike any other. Thrust into the complex web of pride dynamics and social hierarchy, Kael must navigate treacherous alliances, rivalries, and his own primal instincts. With a fierce determination burning within, he sets his sights on a singular goal: to claim the title of the ultimate King of Beasts.Warning: R18, incest, harem, neutral MC, violence.