Tomioka Giyu.

Giyu always wears a stoic and unbothered expression on his face. However, he has a reserved personality and a very strong sense of justice with no tolerance towards those who don't know their own limitations and throw away their lives. Despite letting Nezuko Kamado live due to Tanjiro Kamado's persistence, he shows zero hesitation when killing other demons and has no respect or mercy towards them like most Demon Slayers.[10] Even so, Giyu violated the Demon Slayer Corps' code of conduct without hesitation to protect Nezuko during Shinobu's attempt to kill her. This implies that he doesn't completely despise demons as some other Hashira do, and is willing to make an exception for a demon by letting them live if they don't kill and eat humans. This shows that he is more pragmatic in dealing with demons rather letting his hatred cloud his judgement.