This Ninja Is Obviously Not Strong but Really Hard to Kill - Chapter 6: Devil Bear Kids Series

The story is about a boy entering high school, who answers a strange call from a public phone one night. The caller challenges him to a bet: She’ll remove the birthmark which he sees as the cause of so many problems, and he’ll have fifty days to win the heart of a girl he’d considered far beyond his reach. And with this, a very strange summer begins.

A modern-day antihero, who was infamous for his devious acts, dies in an explosion meant to take down a powerful criminal syndicate. Waking up in a world of sword and sorcery, he finds himself possessing a fragile, powerless body with a strange “System” that seems broken. Initially thinking he's doomed, he learns that by pretending to be weak, he can manipulate others into revealing their secrets, granting him abilities they possess. As he rises in power, he discovers that the System was intentionally sabotaged—by none other than his own future self.

Previously one of the ten greatest Martial Emperor, Gu Feiyang somehow died near the mountains of Heaven Wave.

Fifteen years later, Gu Feiyang crossed through the cycle of rebirth. He was back! But this time, he was in the body of Li Yunxiao. Since then, Li Yunxiao started a treacherous journey. The world is in turmoil once more!

- Description from Novelupdates

Overnight, Tangning became a big slave owner in the southern United States with three large plantations and hundreds of black slaves who could be driven at will.

Tangning was very satisfied with the result of such a time-travel, but then he sadly discovered that he could only enjoy three years of such a good life, because three years later would be the “Civil War”, what should he do after this?

- Description from novelbuddy