Alternative
The Genius Assassin Who Eats Everything / 혼자 다 해 먹는 천재 암살자 / Honja Da Hae Meongneun Cheonjae Amsalja
He is a successful writer who has created a fantasy world in his novel. But he made a terrible mistake in the end, causing the protagonist to reveal himself as a traitor and the world to be dominated by the demon king. He received the wrath of readers and regretted his choice.