I Only Tame Dragons - Chapter 6: Drakha, the Land of the Dragons

Revisit the peak of the Olympian lore.... An eighty year old scholar who has been a fan of Greek mythology since childhood finds himself reborn as the titular ruler of the underworld, the death god Hades after a tragic death. But the gods of Olympus are very much different from what the stories say. He will have to navigate through his new life as a god and prevent a coming calamity... All while not getting caught... How does it feel to be a god in Olympus? A tale into the heart of myths.

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

The protagonist, having degenerated into a “loser” after being unable to find employment, gets caught up in someone else’s attempt to commit suicide-by-train and ends up traveling to another world. The numerous cheat powers he demands from God are all granted to him. But contrary to expectations, these powers bring about disastrous consequences for the protagonist.

Having reincarnated into another world, the optimistic protagonist (Yuuri) starts his(her) heart-warming training days with his(her) teacher.

Once, because of a pair of purple eyes he was scorned. He is a wangye known across the land, cold and bloodthirsty, looking disdainfully upon the world.