Berserk

Since its inception this dark fantasy manga aimed for young adult readers achieved cult status, influencing many video games, comics, and spawning several anime series. Set in european medieval time, it's story about black knight Guts and his adversary Griffith. Guts was born by some unknown woman who died under a tree surrounded by dead people when mercenary leader rescued him. As he grew up he becomes capable warrior carrying huge sword, but after betrayal he kills his savior and joins Griffith's Band Of The Hawk mercenary army. Griffith is fascinating character and in one episode is almost defeated by Guts in a duel. But after some time Gods of the world (clearly influenced by Hellraiser movie) take Griffith as one of his own, who sacrifice his friends along with Guts. From that time Guts travels alone slaying hundreds of monsters and Apostles, very powerful warriors who sold their soul to the Gods in his ultimate goal to kill Griffith who was his friend. Comic itself starts good but after awhile becomes tedious bore.