Worlds Best Assassin 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

An Assassin of the Murim Alliance that inherited the work of a Demonic Cult Leader. He stands up after being down and out, and gets out into the Jianghu! This is the incredible Jianghu journey of the world’s best Assassin, Lee Gwang.