One Piece: Unreal Adventure - Chapter 7: Gaining Weight

He rose from abjection and achieved eternity in glory.
He embraced the prettiest beauties and killed the strongest opponents.
He was able to shift the clouds into rain and cover the sky with one hand.
He could overrun the entire world and go anywhere as he pleased.
He pacified wars and held the world in awe.
He was matchless in the world.
However, his hair turned white overnight for his beloved woman and he was on the verge of death.
He was surrounded by enemies who were trying to take his life.
He struggled his way to become mighty and fought for everything he cherished.
For this age, he was the only king of the Dark World.
His name was a byword for might.
As a man living in the world, his only ideal was to pursue brilliance.

- Description from Novelupdates

The King of Hell sentences you to death by midnight, but I can ensure that you live past morning.

The young man, Qin Lang, received the inheritance of a poison school by chance. He uses poison to kill people, uses poison to save people and he uses poison to chase beauties. With body of ancient extinct poison and a body of a martial artist, he walks around the city, and wanders around in the underworld.

- Description from Novelupdates

In the year 2000, the System arrived on Gaia and changed the world of mankind. The environment became volatile and organisms evolved. To the humans, the System offered a class-base progression with a myriad of skills just like in old RPG games. From magic to bloodlines, as long as people immersed themselves in their passions, the System would incorporate their interests into classes and skills. And with the rise of new powerhouses, old nations were brought down and new ones rose from the ashes, stabilizing and governing their evolved populace.Around 500 years later since the dawn of the System, the story of our MC began. Drai was a musclehead, and his days were mostly spent for two purposes: becoming stronger and tougher! With his single-mindedness and crazy trainings he was finally offered a special class on the Revelation Day. From there on, his journey began. Starting from a prestigious academy and meeting his mentor and new friends, each with their own peculiarities, Drai steadily walked the path of power and invincibility. Party adventures, dark schemes, and veiled threats would accompany Drai throughout his journey.

A new fantasy world built by Fang Xiang, please enter!

- Description from novelbuddy