Board Thread:Versus Debates/@comment-30355627-20161030163643/@comment-25122992-20161211133605

Any form of Sasuke can't be called "weak and uneffective", let alone his highest Rinnegan forms. And no, technically Sasuke was going toe-to-toe with both Kinshiki and Momoshiki individually before the latter's powerup. Given that together they were deemed a danger Kaguya herself feared, I think it's enough for him to battle on pair with Naruto against transformed Momoshiki. Also, it wasn't a suitable matchup for both Naruto and Sasuke to show their full strength, since they greatly rely on ninjutsu, which was restricted in Momoshiki's case, and both of them weren't in their best condition back then, Naruto loosing a lot of chakra because of Momoshiki's attemps to absorb it completely and Sasuke spending some noticeable amount to open the interdimensional portal.