Takatsuki Gentatsu

The Takatsuki's were of the Aizu clan, affluent samurai who opposed the Emperor Meiji and the encroachment of foreigners into Japan. They wanted to restore the Shogunate and therefore their pride, honor, and respect. Gentatsu and Toki were the only surviving members of the Takatsuki family. Gentatsu was old enough to fight, and did so, for the sake of his sister's future. Gentatsu was known as a Hitokiri, which means he was GOOD at it. He was a warrior and a swordsman in a time of swordsmen. As such, he had to be ruthless in battle and win, and to win, he had to kill.

His actions as a Hitokiri injured him, but he had to do it for the future he thought was right. He treasured his family and friends over everything else. He fought for THEM, even though the things he had to do to ensure their future kept him up at night. You get the feeling from Shigure's flashbacks that Gentatsu was actually a gentle person, more of a thinker than a fighter, and was extremely considerate of others- although he was probably no Sakamoto Ryouma, looking out for even the lowest of classes, otherwise he too would have been more sympathetic to the Ishin Shishi.

Gentatsu, as mentioned before, was from a prominent family. This is pointed out by several things: Kenshin recognizes Toki's name as belonging to a samurai family; Gentatsu is respected by the men at the meeting before the strike at the Ishin Shishi meeting, meaning he is an important person in the clan because he seems very young. Even the fact that he had a surname at all pointed to status. (Remember how little Sanosuke asked Sagara-taichou if he could have his name after the war? It's because he didn't have one.)

As for his persona as a fighter, I don't think Gentatsu was comfortable with it at all. He had probably trained as a samurai since a very young age, and had finely honed instincts, but the war gave him terrible nightmares- a mark that he was human, and way out of most Hitokiri's calibur. It was his belief in his cause that kept him fighting. Oh, he had to be good, to even become known as a Hitokiri. But when you're in the same class as Kenshin, Saitou, Okita, Shishio... It wasn't just the passing years that made Shigure better than Gentatsu by the time he himself fought Kenshin in the movie.