Greatest Boss System 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.nl fastest updating comic site. The Summary is

Who is he? Why is he called the Boss? Maybe he’s the fearless ruler of the world. Or maybe the worst enemy of humanity, who tears worlds down. After Su Sin was reborn, he lost all his skills and abilities from former life in a knights’ world. However, a newly implanted System can help him restore them. “My name is Su Sin where Sin means Promise keeper”.