Valkyrie's Shadow - Chapter 1The Paladin of the Holy Kingdom, Part III: Act 3,

The world had started doomsday, and I struggled for a year, before I died under an enchanted beast’s claw. Heaven has given me another chance, back a day before the end happen. Will I be able to change my fate, and that of my loved ones? Now, I will start my journey on becoming the strongest on the planet that the Gods have changed into a game world.

- Description from Novelupdates

In a world where every profession has its own system, one's fate is determined by the job they awaken. Reynard Vale was cursed with the weakest profession—Unskilled Laborer—a dead-end path with no future. Mocked, powerless, and abandoned, he saw no way out.But on the night he chose to end it all, the system intervened.[Congratulations! You have awakened the hidden profession: Jobmaster (SSS-Class)!]Now, with the ability to learn, switch, and master any profession, Reynard is no longer bound by limitations. From boxer to librarian, investigator to world leader—every skill, every class, and every power is his to wield.The world that once looked down on him will soon bow before the ultimate professional.

A young man who had longed for stories of good and evil since childhood lost his life in a tragic accident and was reincarnated as a boy named Chrono Mak in another world.

He learned that in this other world, there is magic and witchcraft, and depending on how you train them, you can become as strong as you want to be, so he decided to become the strongest demon king in order to recreate the story of justice and evil he once dreamed of.