WARNING: The following contains major spoilers for Boruto: Naruto Next Generations Chapter #50, by Masashi Kishimoto, Mikio Ikemoto and Ukyo Kodachi, available now in English from Viz Media.
In the Naruto series, no matter who came at Sasuke and the titular shinobi, they would overcome time and time again. Adversaries like the Akatsuki, Obito, Madara and most notably, Kaguya push them to their limits but no one's been able to outright top them. Even when the other Ōtsutsuki clan members came after them in the movies, the duo beat them, albeit with some occasional help from Boruto.
It's always been clear that their only match was each other. But, Boruto drastically alters this notion because in Chapter 50, Isshiki Ōtsutsuki proves that he's stronger and much more powerful — than Naruto and Sasuke .
To avoid collateral damage in Konoha, Boruto, inspired by Sasuke's old shinobi headband, harnesses the Karma mark and teleports them all to a secret space-time pocket. But here Isshiki proves to be insurmountable, powering up with consummate ease. Naruto and Sasuke have no answers as they try to counter, to no avail. Naruto tries to use the Nine Tailed Fox, Kurama, but his increased chakra blows don't make any headway, either. From his Rasengan to his shadow clones, nothing works, all because Isshiki's shrinking technique basically makes these attacks disappear.
Even when Naruto holds the villain down, Sasuke's Chidori misses because Isshiki simply teleports away. In fact, he's much faster at it than any of the other ninja, perhaps even rivaling Naruto's father, Minato the Yellow Flash. To make matters worse, when the pair rush him, Isshiki unleashes a new technique, dropping black chakra boxes that destroy the shadow clones and render Naruto and Sasuke almost entirely ineffective. They can't attack from afar and now they can't even get close — Isshiki has them in checkmate.
It's the first time Naruto and Sasuke have ever seemed so short of answers and, while Sasuke has his eternal black flame, the Amaterasu, to use, chances are Isshiki will absorb this as well — something that didn't work when Koji Kashin fought him. And if Kurama can't damage him with its massive chakra form, even if Sasuke activates his Susanoo chakra shield, it's not likely to make a difference. The scary thing is Isshiki didn't even prepare for them — he's just like this. And that strategy, or lack thereof, blindsides Naruto and especially Sasuke who wants to end the fight quickly as he has to tend to Boruto's possession by Momoshiki.
But the Konoha ninja aren't getting any openings at all, with the alien reacting and easily turning all their moves against them in ways Kaguya or Madara never could. It's shocking to witness something so one-sided because this back and forth hints Isshiki is toying with the senior ninjas, even using his shrinking technique to steal Sasuke's sword. But with Boruto realizing Isshiki can't — or won't — kill him, he can use this, as well as chakra from both ninja to try to make a dent in Isshiki's armor.