Lets say if somehow any Uchiha with Mangekyou Sharingan evolves to Rinnengan who would be overpowered? The Uchiha would have access to both Sharingan and Rinnengan powers.
Madara was able to use Susano with no eye and 1 Rinnengan eye no problem at all. Sasuke is able to use his Rinnengan and Sharingan techniques.
Madara was able to use Susano with no eye and 1 Rinnengan eye no problem at all. Sasuke is able to use his Rinnengan and Sharingan techniques.