MTL - I, The Grandson of Garp, Scared Luffy Into Tears - Chapter 729

In the year 2220, a radiation source in the Pacific Ocean, tens of thousands of times stronger than a nuclear bomb has begun mutating exposed creatures into horrific monsters thousands of meters long. Mankind’s only hope was nuclear weapons, which only made matters worse. The combination of the natural radiation and nuclear radiation released an incurable and highly infectious virus, turning the 90% of the world’s population into violent zombies in mere weeks.

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

Should an untalented guy like me die?Then I’m going to die.I will die as you so desire.After dying, I will challenge the world again.Until I kill this tr*sh-like world!

Found a suitable body named Bai Xiao. Reincarnating into the World of Elementalists.

“Mission: Overpopulation of carnivorous fish in the lagoon.

Please kill 666 carnivorous fish in order to prevent the destruction of the lagoon’s ecosystem.

Reward: 20 Balance Points.”

“Mission: Forest fire.

Extinguish the fire.

Reward: 200 Balance Points.”

- Description from Novelupdates