One Piece: From the Rocks Era to King of the World - Chapter 1 - . Li Yuan travels through time and kills people

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

In a shocking turn of fate, Jack Anderson's life is brutally cut short. But death isn't the end for Jack; instead, it marks the beginning of an extraordinary journey.Reincarnated in a mystical realm, Jack discovers he's been gifted with incredible powers and an enigmatic system that guides his every move. As he navigates this unfamiliar world, Jack must confront formidable enemies, unravel ancient mysteries, and unravel the secrets of his own destiny.With the undead system as his trusted ally, Jack embarks on a perilous quest to unravel the truth about his past, his newfound abilities, and the hidden forces manipulating this strange new world.Will Jack master the undead system and unlock its full potential, or will the shadows of his own mortality consume him? Dive into the world of 'The Undead System' to join Jack on his heart-pumping, action-packed adventure through the realms of the unknown.

Takebayashi Ryouma, a 39 years old man with hidden past, found himself in a strange white room. The gods tell him that he has died and that they are sending his soul to a different world, a world where magic exists. After living alone for 3 years, his gamer soul loses its common sense and starts along crazy routes.