Itai no wa Iya nanode Bōgyo-Ryoku ni Kyokufuri Shitai to Omoimasu - Chapter 9

The ordinary yet not so ordinary detective, Wen Wen, woke up in a mental hospital and discovered that his right hand was connected to a mysterious space called the 'Catastrophe Containment Facility,' from which he could acquire the powers of the monsters imprisoned within!By capturing a vampire, he gained a formidable physique;By capturing a ghost, he could turn invisible and pass through walls;By capturing a fox spirit, he could charm the opposite sex...In short, in order to obtain more powerful abilities, Wen Wen began to diligently capture monsters, thereby stepping into the strange world of superpowers and seeing the hidden truths behind the curtain...

A 40-year-old man suddenly dies and is reincarnated in a world devastated by zombies—but instead of becoming a hero or a survivor, he wakes up as a zombie girl.

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