MTL - Warhammer: The Beginning is the Crisis of Annihilation - Chapter 341 The Flying and Prosperous Constantine (subscription required)

Nicholas Crowley is used to scraping by in a world where magic is dying. The modern age has left the arcane behind, and the few remaining practitioners fight over scraps like starving dogs. That, however, is no longer his problem. While performing a ritual, something interferes, and his soul is ripped from his body. He awakens during the Class ceremony as Nick, a kid living on the frontier of the Green Ocean, a seemingly infinite expanse of trees brimming with rare ingredients and powerful creatures. Mana is abundant here, and the omnipresent System allows for feats he had once thought impossible. And yet, not everything is as rosy as it seems. Legends walk the land, and Gods require their due. Will his experience as an Occultist be enough to navigate this wild new world?

A lifetime ago, Chu Xun was shackled and thrown in jail on false charges. For three whole years, he suffered extraodinary torment from his cellmates every day. Even though he had escaped death many times, he still died from his cellmates’ fists the day before he was to be released.

After death, Chu Xun transmigrated to a different world of cultivation, where cultivation was the one true path. Carrying the weight of his hatred, Chu Xun began to cultivate in hopes of becoming an Immortal Emperor, who could manipulate heaven and earth and travel through time. After painstaking cultivation of three thousand years, he succeeded. Then he sacrificed all his cultivation without hesitation and returned to the day before he was to be released.

This life, he wanted to find out the truth and the one behind his murder in last life. He would continue to cultivate and strengthen himself so that the tragedy would not repeat itself. He wanted to master his own destiny.

In this life, what people would Chu Xun encounter and what experience of love and hate would he have with them? What difficulties would he encounter and how would he overcome? The answer is the book.

- Description from Novelupdates

Following a brutal and tortured death, a former assassin, known only by his codename Kuro, is given the opportunity to reincarnate in another world, a world with magic and monsters. Armed with an unrivaled healing factor and an inhumane pain threshold, Kuro opts to go for a reckless direct approach in this world instead of a stealthy and cautious one, and as a result, slowly gains attention bit by bit.

Having previously been a loner in his old life, he interacts and befriends people for the first time in his existence, however, his blunt nature also sees him making just as many enemies, both big and small. By combining his old assassin skills with the magic powers of this world, along with his high resistance to pain and rapid regeneration, he doesn't take long to establish himself as a formidable force in this world.

Initially, Kuro only faces minor threats, like weaker monsters and bandits. But before too long, the threats slowly but surely become more and more severe…from Zombies to a bloodthirsty empire to Vampires and Demons, and even divine beings…however, as the enemies he faces grow stronger, so does Kuro, gaining rare powers that have never or rarely ever been seen in this world…