MTL - The Fallen Merman - Chapter 105

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

Yi Jiamu was a patient with the ‘Ability Deficiency Disorder’ and he inadvertently attracted Gu Yesheng’s attention.

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.

When an era came to an end, various forces set foot in cultivation to compete for immortality. A young boy who spent most of the time sleeping got lucky in the troubled times and became an unparalleled immortal who could cover the sky with a snap of fingers. Was he going to live forever?

- Description from Novelupdates