Toaru Majutsu no Index - Volume 10, Chapter 8: The Reason for the Clenched Right Fist. Light_of_a_Night_Sky.

On the Continent of Heavenly Pulse, martial arts is revered, and the strong reign supreme. Young Master Chen Shaofeng used to live a carefree life, but an engagement forced him onto an unconventional path. With the Mountain and Sea Diagram, he obtains a heritage that shocks the world, builds a dominant path, treads on the Heavenly Pulse, breaks the heavens and earth, and achieves the peak as a War-god.

TL Description: Eat The World Tree is about a strange guy, who happens to be extremely curious and unable to stop himself from acting on his curiosity. The MC makes a slight mistake and travels to another world, and must fulfill specific quest or face varying levels of consequences (normally death).

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

“I don’t care what Thanos’ ideals are, and I don’t care what the consequences of having too many creatures in this universe will do, as long as he doesn’t ruin my business with that damn Infinity Glove!” – Kahn Ponte

Once he traveled to the world of American comics, Kahn had the golden finger to trade all worlds.

At this point, the name of Boss Kahn not only resounded in the Americas of the Marvel Universe, but his influence spread to all the worlds!

PS: There are many follow-up worlds such as Marvel, Naruto, Harry Potter, One Punch Man, Black Robe Pickets, Dragon Ball, Pirates, etc. You can decide…

- Description from novelbuddy