Isekai Maou to Shoukan Shoujo no Dorei Majutsu - Volume 1 Chapter 1.10

She is the legendary queen of mercenaries whose name daunts even the big shots in society. With an ancient jade pendant in her hand, she is great at almost everything, be it seeking the truth or the art of healing.

In this brutal world ruled by the law of the jungle, Ximen Wei is driven by his desire to return home and escape his past regrets and feuds.

As he becomes increasingly obsessed with achieving his goal, he loses his emotions and humanity, resorting to any means necessary, no matter how unscrupulous or immoral.

He becomes a symbol of massacre and death, a demon god feared throughout the Qi World for his willingness to kill anyone who stands in his way or possesses something he needs.

Follow Ximen Wei's journey as he rises to power, terrorizing those around him in his quest to become a powerful demon god.

Witnessing her boyfriend cheating on her with her bestie, Shiyao was so angry that she went to a pub for fun and met a man, who was really a piece of work. After a crazy night she fled away, but was embarrassed to know that the man she slept with was her boss You Ze.
Jesus, give her a break!

- 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…