The Player Hides His Past - Chapter 604

In the twilight years of the dynasty, treacherous villains rose to power and demons plagued the world.Qin Zheng, bearing a scroll of virtuous deeds, traveled through time and found that by beheading those wrapped in sin, he could attain virtue and enhance his martial arts prowess.Thus, Qin Zheng glanced at the Ghost Head Greatsword in his hand.“The auspicious moment has come, to the execution!”With a great shout, Qin Zheng swung his blade and beheaded his target!!----------------This book is also known as “I've Become an Executioner After Time Travel?” and “Achieving Sainthood Through Merit, I Seek Elevation by Executing Sinners”......

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates

A 20-year-old genius medical student transmigrated to a book she read during an experiment and became a female supporting character named Mo Li.