Rurouni Kenshin
He is also, somehow, kind of a goofball.
Produced by Studio Gallop and directed by Kazuhiro Furuhashi, Rurouni Kenshin aired on Fuji TV from 1996 to 1998. Ninety-four episodes built around one of the great premises in shonen anime: a man defined entirely by violence trying to build a life around its opposite. The Kyoto arc, Kenshin versus Shishio Makoto, a man burned alive by the same government Kenshin killed for and left for dead, is one of the finest extended story arcs of the 1990s. Shishio is one of the greatest villains the genre has produced. The final duel delivers.
In the West it was packaged and sold as Samurai X, a marketing decision that aged about as well as you would expect. The fansub community knew it as Rurouni Kenshin. That is what people were downloading. That is the version people kept alive.
The Trust & Betrayal OVA, four episodes depicting Kenshin's origin as the Battōsai, is a separate and devastating masterpiece. Watch the series first. Watch the OVA after the Kyoto arc. Do not watch the Reflection OVA without emotional preparation.
Note: avoid the filler arc that closes the TV run. The manga never finished it. The anime invented an ending that goes nowhere. Stop after episode 62. Everything you need is there.
Guides and reference pages for this series. More coming.