In chapter 658, it's said that "Right eye returns to rightful owner". Which proves it was transplanted to
However, something interesting happened when he was resuscitated using the Samsara of Heavenly Life Technique. During the process, his eyes crumbled. This is because when a person is revived through this technique, they have the same set of powers that they had before they died.
When Madara's over-usage of his Mangekyō during the Warring States Period left him blind, this prompted his brother, Izuna Uchiha, to bequeath Madara his eyes on his deathbed for the sake of preserving the Uchiha, thus granting Madara the Eternal Mangekyō Sharingan.
A descendant of the Uzumaki clan like Naruto, Nagato's Rinnegan is later revealed to have belonged to Madara Uchiha, who transplanted his eyes into the child as part of his plan. Nagato desires peace for the world, helping Yahiko to create the Akatsuki to achieve that shared dream.
His entire body was revived into the living state via Rinne Tensei, but since these were fake eyes and his actual Rinnegan eyes were still somewhere else (the left eye was owned by Obito and the right one was hidden), it left Madara without any eyes at all until he got them back again.
He transplants his Rinnegan (輪廻眼, lit. "Saṃsāra Eye") eye power into a child named Nagato, a member of the terrorist organization Akatsuki, to be preserved for his eventual revival years later.
In order to gain access to the other dimension, Madara stole Kakashi's Sharingan, thus stripping Kakashi of all of its powers.
In order to awaken the Rinnegan you must have the Uzumaki clan chakra or have the Hagoromo Otsutsuki chakra. All Uzumaki clan Rinnegan users have different six path abilities.
Made famous by the Uchiha clan, Mangekyo Sharingan is one of the most bloodline feats in the Naruto series. These are its strongest abilities. The Mangekyo Sharingan is the evolved form of the Sharingan and one of the strongest known Kekkei Genkai in the entire Naruto series.
In the Fourth Great Ninja War, Sasuke Uchiha, who was already the reincarnation of Indra Otsutsuki, met Hagoromo after he was in a near-death state. Just as with Naruto, Hagoromo gave half of his chakra to Sasuke, which led to his left Sharingan turning into a Rinnegan.
One such element was Madara's EMS ability – the power to reverse time. The animation showed Madara's EMS spinning uncontrollably, resulting in everything moving backwards. This was revealed to be time reversal, a direct ability of his Eternal Mangekyo Sharingan.
After implanting Hashirama's DNA into his body and Kabuto Yakushi's further experimentation, a replica of Hashirama's face appeared on the left side of Madara's chest.
Amaterasu is a Mangekyo Sharingan ability used by Itachi Uchiha and his brother, Sasuke Uchiha. In both cases, Amaterasu is accessible through the left eye. When used, this ability immediately burns the target with black flames that cannot be extinguished until they burn to a crisp.
Sometime between Madara's death in his battle with Hashirama and the time delayed Izanagi Madara used to resurrect himself, Black Zetsu found out where Madara's body was hidden and hid itself inside Madara's body.
Hashirama Senju, aka the First Hokage, was the only one who could ever beat Madara Uchiha in life. In death and resurrection, Madara gained access to powers he could never gain in life. However, the First Hokage did famously beat Madara in a duel at the Final Valley and seemingly killed Madara.
Obito Uchiha gained the Rinnegan after Nagato Uzumaki died. Strangely, having both eyes was too much for his body to handle, so he only implanted one Rinnegan into himself. Nonetheless, Obito's usage of this eye was quite great.
One of the Three Great Eyes in Naruto, the Rinnegan is the strongest eye of them all. It was first said to be wielded by Hagoromo Otsutsuki, the Sage of Six Paths.
Izuna Uchiha
Still, his Mangekyō abilities never reached their full potential and he tragically fell in battle at his rival's hands.
Kaguya's nine tomoe Rinnegan sounds like the most powerful, since it can cast Infinite Tsukuyomi and Dimensional Shifting. About Sasuke's six tomoe Rinnegan and Hagoromo/Madara's purple Rinnegan, I think they're tied.
The only two ways Naruto can get the rinnegan is through blood transfusion from Sasuke or absorb enough of Sasuke chakra and merge with his chakra.
It is possible for Naruto to Awaken the Rinnegan. I have come to the conclusion in which Naruto Uzumaki is capable of awakening the Rinnegan through DNA infusion similar to that of Madara Uchiha's way of awakening his Rinnegan by infusing Senju DNA which he acquired through Hashirama Senju with his Uchiha DNA.
There is no doubt that Kakashi is quite strong despite the loss of Sharingan. He is by no means weak and can hold his ground against tough opponents. Whether it be his ninjutsu, taijutsu, or shuriken jutsu, Kakashi has mastered them all.
Itachi ended up giving Naruto the crow, which had Shisui's eye. Itachi later explained the significance of the crow to Naruto. He stated that he programmed the eye on the crow to use Kotoamatsukami on the person that takes Itachi's Mangekyou Sharingan.
A young Kakashi had his original left eye cut out by an enemy Stone ninja while he was protecting his teammate Obito; this is also how he got the scar running vertically along his eye. At around this same time, Obito unlocked his Sharingan, used it to kill their enemy, and saved them both.