Metropolis strongest mad soldier 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

He is a Humanoid weapon, but both good and evil, good because he can protect his family for all directions, evil because he can be a sword that go west that flow a river of blood. When such a demon character returns to the city after being released from prison, facing all kinds of beauty and the bustle of the flowers, how will the gorgeous sparks rub off? The world will be unmatched!