WARNING: The following contains spoilers for Chapter #54, “Bro,” of Boruto: Naruto Next Generations by Masashi Kishimoto, Mikio Ikemotot, Mari Morimoto and Snir Aharon, now available in English from Viz Media.
In Boruto, one of the biggest moments was when Naruto's son created the Vanishing Rasengan. It initially seemed like he couldn't master one as powerful as the Hokage and his predecessors like Minato because of his age. Still, Boruto pushed on in training, with Sasuke guiding him on how to perfect it or least make one that would be worth using in battle.
Eventually, the wily teen was able to come up with a unique Rasengan. Even Naruto was left in awe, making Sasuke a truly proud mentor. Unfortunately, in the latest manga chapter, this Vanishing Rasengan comes back to haunt Sasuke as he's hit with one that nearly kills him.
A while back, Sasuke taught Boruto about changing the nature of chakra, which leads to him infusing Wind and Lightning Style to upgrade his Rasengan. As it glides, the nature transformation suddenly activates, causing it to disappear from sight, which could trick an enemy into lowering their guard. They'd think it faded away but it was always continuing to its target, adding an element of surprise.
And it's used to perfection when Momoshiki invades. It damages the alien badly and it's here in the field Sasuke names it as the Konoha ninja go on to successfully fight him off. Boruto would later deploy it against the Mujina Bandits, although his arm's still damaged from the Momoshiki fight and the Rasengans he generated, so he can't deploy as many as before. Come Chapter 54, the move returns, but this time it isn't Boruto throwing it -- it's Momoshiki, who has possessed the boy.
With Naruto out cold, Sasuke and Kawaki formulate a plan to stop Momoshiki. They don't want to hurt Boruto's body but they're out of options. Luckily, Sasuke deduces that Momoshiki can't absorb any of their techniques, as he doesn't want extra chakra coming into his vessel to awaken Boruto's consciousness. But it's here Momoshiki decides to use a sneak attack from behind a rock. As Sasuke confers with Kawaki, he senses something coming but it's already too late. The Vanishing Rasengan has reappeared and, seeing that it was thrown by an Ōtsutsuki, Sasuke can't block its greater speed. The energy ball cracks the Uchiha Ranger directly in the chest, leaving him reeling in pain, barely able to recover.
Momoshiki admits he's too weak to make it as lethal as he'd have liked but it's already done a massive amount of damage to Sasuke's vitals. Had anything about Momoshiki's attack been slightly different, had Sasuke not flinched or moved at the right time, it could have been a decisive blow. That said, it's a cruel fate that Sasuke gets put down by something he helped make, leaving Kawaki at Momoshiki's mercy.