Madara Uchiha and Kaguya, who were by far Naruto's most powerful villains, both made the show worse instead of elevating it. While Madara was mentioned in Naruto Shippuden's first episode, it was only in the latter half of the show that the character finally appeared. It took even more time for Kaguya to be introduced: the all-powerful alien creature only showed up in Naruto Shippuden episode 460. And yet, by the time of their respective introductions in the anime, these characters subtracted from the show rather than adding to it.
Well-developed, almost sympathetic villains have always been one of Naruto's strengths. The very first two villains in the series, Haku and Zabuza, already showed how Naruto would treat its antagonists: they were real people with sincere motives and who could even be redeemed. Naruto Shippuden's time jump expanded the universe in a significant way, but the villains remained a highlight of the show. While not as redeemable and sympathetic as the villains in Part 1 of the anime, each of the Akatsuki members received enough screen time to be developed in a way that made them even more menacing.
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Contrary to all those qualities, Madara Uchiha and Kaguya were introduced as being so absurdly powerful that they often seemed more like a video game final boss than actual characters, and this diminished their impact on the story. Madara collected almost every special technic Naruto had established, including but not limited to Rinnegan, Perfect Susano'o, Wood-Style, Rinne Sharingan — not to mention infinite chakra, immortality, and the ability to become the Ten-Tails Jinchuriki. Kaguya managed to be even more overpowering, as the
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