In Naruto, Indra and Asura are the sons of the Sage of Six Paths, Hagoromo Otsutsuki. As a result, they were both immensely powerful and became the progenitors of the strongest clans in the show. Unfortunately, instead of working together, the pair ended up becoming enemies. After their deaths, their power seemed to enter other people to continue the curse of the two brothers fighting each other. This has resulted in quite a few incarnations of both Indra and Asura, but only four are shown in the series.
Note: This article contains spoilers for the Naruto series.
Every incarnation of Indra Otsutsuki in Naruto
Indra Otsutsuki is the first born son of Hagoromo Otsutsuki. He was considered a prodigy and used his father's teachings of ninshu to develop modern day ninjutsu. Indra was on a path to success, but it all came crashing down when Hagoromo chose to make Asura his successor instead. His bitterness and hatred made him vulnerable to Black Zetsu's influence.This resulted in Indra beginning the Curse of Hatred for every Uchiha Clan member that came after him.
1) Madara Uchiha
Madara Uchiha was the earliest incarnation of Indra Otsutsuki featured in the show. With his mastery in using the Sharingan, he instilled fear into the hearts of many Shinobi. Madara also became the Ten-Tails Jinchuriki during the War Arc. This caused Madara to become practically unstoppable as Team Seven never got close to beating him while in this form.
2) Sasuke Uchiha
Sasuke Uchiha is the deuteragonist of the Naruto series and Naruto's greatest rival. In Naruto Shippuden, he was revealed to be the latest incarnation of Indra Otsutsuki. The animosity Indra held for Asura seemed to manifest in Sasuke throughout Shippuden.
Sasuke's desire for revenge and hate towards Naruto led to him defecting from the village on a quest for more power. This caused him and Naruto to fight many times as Naruto always tried to bring him back to the village. However, in the end Sasuke found his way back to Konoha and the two ended the fight between Indra and Asura.
Incarnations of Asura Otsutsuki
As Hagoromo's second son, Asura was the younger brother of Indra Otsutsuki. He did not display any prodigious capabilities when he was younger, but he was incredibly caring and empathetic, which caused Hagoromo to make him his successor rather than Indra. He is the progenitor of both the Uzumaki Clan and the Senju Clan. Asura is also one of the only natural Wood Release users in the entire series.
Hailed as the God of Shinobi, Hashirama Senju was the first incarnation of Asura Otsutsuki shown in the series. He was a master in a diverse set of Jutsu, including Sage Mode and Wood Release, and the only person capable of matching his power was Madara. Unfortunately, he was not able to accomplish what Asura wanted and break the curse, causing him and Madara to fall out of a friendship and constantly fight.
Naruto Uzumaki is the most recent incarnation of Asura Otsutsuki and is sometimes referred to as the Child of the Prophecy. Unlike Hashirama, he was able to successfully break the curse that made the incarnations of Indra and Asura fight each other by convincing Sasuke to come back to Konoha. In Boruto, Naruto is the Hokage and Sasuke is his partner; whenever the situation calls for it, the pair work together to take down anything that threatens Konoha's safety.