Ya know, there's just some anime that have that absolute badass beyond badass, right? Well I thought I'd give credit to the badass with a blade that I think could even show Kirito a thing or two about it. And that would be (drumroll) Kenshin Himura!!
I mean what's not to love about the guy, he has the power of an army, the heart of a hero and the skill of a top assassin. (also if you pay attention, he knows quite a bit about the law system and its workings)
Though his past is extremely traumatizing, he worked hard to become who he is today, from joining the military at a young age, to learning a sword style that no one else (except his master Hiko) knows. Not to mention conquering his other half, the Battousai personality.
After many years of fighting and killing, he swore never to kill again after the loss of his wife and left to start over again. And in time, found new friends which became family.
Full Story: http://kenshin.wikia.com/wiki/Main_Page
Hope you all enjoy. :)