Terminally-Ill Genius Dark Knight is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

[By the author that brought you !] is a fantasy RPG infamous for its extreme difficulty. However, to Yoo Chan, who was diagnosed with a terminal illness at a young age, this game was his entire life and has now become his reality. From now on, Yoo Chan has to survive in this world as Nox von Reinharber, the worst villain in the first act of the game. Will he be able to reach the end of the story safely?