Hidan is an S-rank missing-nin who defected from Yugakure and joined the Akatsuki. There, he was partnered with Kakuzu. He was also the second newest member of Akatsuki at the time of his introduction. Kisame Hoshigaki laughingly referred to Hidan and Kakuzu as the Zombie Combo, because of their seemingly incredible inability to die.
I say that Hidan is an S-rank missing-nin because while he was blown to bits by Shikamaru, he is an immortal who can only die from lack of nutrition. While it can be assumed that enough time has passed to have killed him, I cannot be sure so I prefer to say he IS still alive.
Hidan, for a lack of a better phrase, was a psychopath who did dark rituals to worship a god called Jashin. His religion called for the perfect and utter destruction of everything. Ironically enough, Hidan, unlike the majority of Naruto characters, doesn't seem to be a byproduct of a violent world. He actually abandoned and turned on his village because it decided to abandon the shinobi world and turn into a peaceful industrial village. His village's call for peace is actually what triggers his insane thirst for murder.
Hidan first truly appeared in his extended fight against Shikamaru and Asuma. It was actually Hidan who kills Asuma, Shikamaru's beloved sensei. Hidan while a very gifted fighter, nimble and strong enough to wield a Triple-Bladed Scythe easily in battle, did not look to strategize or outthink his opponents because he knew he was immortal. This style of rash fighting often got him in trouble, as when he faced off against Asama and was beheaded. He eventually, however, had his head reattached by his partner, Kakuzu, and continued the fight.
His main style of attack was making a cursed connection between himself and his opponent. He would step into a ritual circle, and having consumed some of his opponent's blood, would go about mutilating his own body. The cursed connection made sure that, while Hidan was in the circle, any damage inflicted upon his body would also be received by his opponent. Eventually he used this style to impale himself through the heart while connected with Asuma, thus killing Asuma.
Hidan met his untimely "end" at the hands of Shikamaru in their next encounter. Shikamaru used his shadow connection to separate Hidan from Kakuzu and take him to an enclosed forest area surrounded with wire and explosive tags. Shikamaru had prepared the area in advance. Hidan attacked Shikamaru once Shikamaru's shadow bind wore off, and was able to draw Shikamaru's blood. He consumed it, and again impaled himself and seemingly killing Shikamaru. Shikamaru, however, reveals that he did not consume Shikamaru's blood, rather the blood of Kakuzu, thus killing one of Kakuzu's hearts.
As Hidan tries to attack Shikamaru again, Shikamaru binds him with his shadow technique. Binded, Shikamaru covers Hidan with the surrounding explosive tags and blows him to pieces. As an act of revenge, Shikamaru uses Asuma's lighter (in the anime, or a cigarette in the Manga) to light the explosives.
All I can say is that was one psycho character. But it was nice to finally dislike a guy in Naruto, without having to feel bad about his sad history haha.