Peerless Little Immortal Doctor - Chapter 33 - : Policewoman Li Qinqin

Shen Yuan, a normal human who was living his life peacefully on earth died mysteriously, only to get reincarnated into the world of cultivation with an unknown bloodline so powerful that it even surpassed his chest system....“Hmm, looks like becoming an alchemist might be good. System, purchase the Alchemy knowledge.”[Ding!][Congratulations Host, for acquiring Heaven Refining Alchemy Sutra.]...Follow to see the journey of how Shen Yuan creates the strongest harem since the Primordial times to journey the three thousand world.

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

After crossing over to Naruto World, Shiranui Yuuji found that there was an incomparably terrifying Godzilla in his body.

“You are Tailless Bijuu? Your chakra is astonishing…. What a coincidence, so am I.”

“You know Bijuu’s coat? I don’t have Bijuu’s coat, but I do have Godzilla Coat-”

“Bijuudama is terrifying!! It can destroy a mountain as soon as he sends it down?”

Hiss, that Bijuudama scared Yuuji, he quickly moved his hands to form seals,

“Nuclear Release – Atomic Breath!”

When Yuuji turned into Red lotus form, Godzilla pressed Nine-Tailed to the ground.

“Nine-Tailed, your strength is too strong. You need to be fried…”

Nine-Tailed, “?”

“What Jinchuriki are you exactly?”

This novel is also known as I Possessed a Demon Sovereign

Chen Luoyang felt that something was wrong with his transmigration. After transmigrating, he possessed the body of the highest expert in the world, the Master of the Demon Cult, addressed respectfully as the Demon Sovereign.

Generally, aren’t supreme experts the ones that leave behind a wisp of their soul behind and occupy a new body of some miserable low-level youngster then they go on a journey of revenge and make a comeback?!

Or perhaps it would be transmigrating into a miserable youngster’s body and obtaining a cheat slowly walking the road to becoming a God?

But why did his transmigration seem wrong?

Now my environment is full of big shots and I feel like I’m going to be exposed!

- Description from Novelupdates