personality:Nagato was a sensitive but kind boy, prone to crying, and was traumatized by the idea of killing others, even to save his friend Yahiko. Scared and unsure of his place in the world, he desired to help those he cared about, but never knew how. Nevertheless, he was a talented and gifted student, mastering every technique Jiraiya had taught him. He was consistently respectful and kind to Konan, who he claimed to be his "angel" in Amegakure. He was shown protecting her, without request or hesitation, from Jiraiya, before his battle with his former teacher. Apparently, she was the only Akatsuki member that addressed him by his names, Pain and Nagato.
As Pain, his personality was very different, having become a calm, serious, aloof, and detached man. Apparently believing traumas he experienced in his youth had enlightened him to the true meaning of pain and suffering, he considered himself a deity, and believed he had evolved beyond a mere human being. He sought to show the world the meaning of pain by using an ultimate weapon to deter future wars, by means similar to "mutually assured destruction", and showed no moral qualms about his actions. He was willing to kill Jiraiya to ensure the completion of his plans. He even went so far as to proclaim himself a "god of peace", that had to guide the world to maturity through pain. Finally, he felt that no-one could understand true peace unless they understood "true" pain, something his childhood friend Yahiko believed. Minato Namikaze believed Madara Uchiha to have been using this philosophy in his favor, in order to manipulate Nagato.
Nonetheless, he was seen to be quite respectful, particularly to the fallen and the dead. Given the Akatsuki members' frequent bickering, he often restrained them, and encouraged better relations among members. He even suggested that they mourn for Deidara after his passing, and reprimanded Kisame for calling Hidan and Kakuzu the "Zombie Brothers". After his battle with Jiraiya, he held a moment of silence for his former teacher, out of respect for his power.
Because Konohagakure was partly responsible for the tragedies in his life, he held some animosity for the village. Although Jiraiya's influence improved his opinion of the village during their time together, he eventually came to believe that Konoha profited from the tragedies of others and hated it and his former teacher.
During the Second Great Shinobi World War, Nagato lived with his parents in a village near Amegakure. One day two Konoha shinobi broke into their home looking for food, unaware that the place was still inhabited. Nagato's parents, believing they were going to be killed, attacked the two so that Nagato could escape. Having mistaken them to be enemy ninja, the Konoha ninja killed his parents. In his grief, Nagato awakened his Rinnegan and killed the assailants. He would come to consider this incident the first great pain of his life.
His family gone, Nagato wandered the country, going from house to house asking for food. In time he met a dog named Chibi and later, Konan and Yahiko, who began traveling with him in his search for food. One day, Chibi was killed in the crossfire from Hanzō's fight with the soon to be Sannin. Nagato mourned his death. Soon afterwards the war ended, and the three orphans ran into the Sannin. Rather than return to Konoha with his teammates, Jiraiya decided to teach the three how to look after themselves.
The Ame Orphans
Soon after Jiraiya began living with the orphans, Nagato and Yahiko were attacked by an Iwagakure ninja. Nagato reactivated his Rinnegan to defend Yahiko, killing the ninja. When Jiraiya found out about this, he decided to train them in ninjutsu. Nagato was very emotional about killing the ninja, and asked Jiraiya for help so he could protect Konan and Yahiko. Jiraiya's response was for Nagato to grow up and to use his eyes to find the peace that they both desired for the world. Three years later the orphans had become competent ninja, so Jiraiya returned to Konoha.
Over the years, news of the three's exploits would reach Jiraiya. This often consisted of the death of someone who opposed them; eventually he received word that they had all died. In truth, Nagato, Konan, and Yahiko began a quest to find peace. They became full-fledged Amegakure ninja and gathered followers who shared their philosophies of an end to war. The leader of Amegakure, Hanzō, viewed the group as a threat to his position as leader and schemed with Konoha's Foundation to eliminate them. Claiming to want to discuss peace, Hanzō lured Nagato, Yahiko, and Konan to an ambush. There he forced Nagato to choose between killing Yahiko or Konan. Not wanting to force Nagato to make the choice, Yahiko impaled himself with a kunai, and placed that very kunai in Nagato's hand. With Yahiko's dying breath, he told Nagato to survive, because he believed in Jiraiya's words that Nagato would become the world's savior. This would become the second great pain of Nagato's life.
Devastated, Nagato retrieved Konan and Yahiko's body and launched an attack against Hanzō's men. With the Summoning: Demonic Statue of the Outer Path he was able to kill all but Hanzō. However, the technique left Nagato emaciated, with numerous chakra rods embedded in his back. He severed his loyalties with Amegakure by scratching through the symbol of his Amegakure forehead protector, resolving to teach the village and the world his pain. Yahiko's body would later be incorporated into the Six Paths of Pain as the Deva path.
Upon adopting the alias "Pain", Nagato led the rebelling forces in the Amegakure civil war, and took control of the village by assassinating Hanzō. He then solidified his leadership by systematically killing anyone who had direct ties to the former leader. At some point he assisted Madara Uchiha in the creation of Akatsuki, using Amegakure as his base of operations
Nagato's incredible power stemmed mainly from his Kekkei Genkai, the Rinnegan. This was originally possessed by the Sage of the Six Paths, the world's first ninja, and the founder of modern ninjutsu. The Rinnegan's abilities are largely unknown, but it did permit the user to use all types of elemental chakra, and allowed Nagato to master every technique Jiraiya taught him. It also enhanced his vision of chakra in a similar manner to the Uchiha clan's Sharingan and the Hyūga clan's Byakugan, allowing him to see the chakra of barrier techniques around the perimeter of his location, and the chakra gathered at a shinobi's feet. According to Ibiki, the Rinnegan allows Nagato to use any technique he wishes.
 Six Paths of Pain
The "final" Six Paths of Pain.
Main article: Six Paths of Pain
Nagato's most powerful and most used technique was the Six Paths of Pain (ペイン六道, Pein Rikudō). This technique allowed Nagato to control six separate bodies as though they were his own. Each of these bodies were reanimated corpses that were both kept mobile by and made use of Nagato's chakra. While controlling them, Nagato used the alias "Pain", yet still regarded them as separate entities from himself.
In order to use the technique, Nagato remained in a machine, that moved with six relatively small mechanical legs, and used several large chakra rods on his back to transmit chakra. From that point, the chakra was picked up by the numerous receivers, modeled as body piercings on each body. To control them, Nagato had to be close by, and ideally at the highest possible point, so he could have the best possible range.
Based on the six Buddhist paths of Reincarnation, each body was named after the one of the different "paths": Deva, Asura, Human, Animal, Preta, and Naraka. The only common feature shared by these bodies was their bright orange hair and Rinnegan eyes. Each also had a vast number of body and facial piercings of various shapes, sizes, and patterns. Each body seemed to serve a specific purpose in battle, such as summoning, repairing, and defensive capability.
Nagato's main body acts as the seventh path of pain, capable of controlling life and death. This path is referred to as the Outer path. Nagato is also able to use the powers of the other six paths, as they are all powers of the Rinnegan.