In the Naruto-verse, few powers are as iconic as the legendary eye techniques that certain characters possess.

In Naruto and Boruto, Sasuke Uchiha is one of the strongest Uchiha who possesses great power and the Rinnegan. Yes, he does indeed lose his Rinnegan.

Madara could have easily been the greatest shonen villain, if his character progression was the same as Sosuke Aizen from Bleach.

According to this Naruto theory, Kishimoto wrote Neji as a potential Akatsuki member but dropped the ideas due to his similarities with Sasuke.