In 1989 my roommate and I got mixed up in the US comic book rebirth. One of the books that got printed during this time was an English version of the graphic series Lone Wolf and Cub originally done in Japan in 1970. Years later there was a rebirth of Samurai movies and many movies that had never been released in the US were released. One series released during this time was a series made starting in 1972 based on the Lone Wolf and Cub graphic series. As soon as I saw that these existed I wanted to see them and I was not disappointed, they are fantastic.
There are six films in the series: Sword of Vengeance, Baby Cart At the River Styx, Baby Cart to Hades, Baby Cart in Peril, Baby Cart in the Land of Demons, and White Heaven In Hell. These movies have fantastic cinematography, fantastic musical scores (very 70's), are extremely violent (definitely not for kids), and wonderfully acted and directed. There is definitely nothing bad to say about these movies, though they are certainly not for everyone.
I think a lot of times what is hard in movie adaptations is to capture the spirit of the novel. This movie series captures it perfectly. The vileness of the Yagyu clan, the brilliance and misery of Ogami Itto, and the innocence of his child. I cannot recommend this series enough, but again warn against the extreme violence.