The following contains spoilers for Boruto: Naruto Next Generations Chapter 69, “Captives,” by Masashi Kishimoto, Mikio Ikemoto, Mari Morimoto and Snir Aharon, now available in English from Viz Media.
One of the most sentimental aspects of the Naruto series was how Naruto didn't want to kill Sasuke. He didn't care who was the Hokage, which other Konoha-nin felt the last Uchiha kid was a threat, or even that Sasuke would attempt to murder him on sight. He held true to the belief that Sasuke could be redeemed and the monster inside him would be exorcised.
After all, Naruto grew up misunderstood too, so if he could get Sasuke to forgive the Hidden Leaf for eliminating his clan by using his brother Itachi, they could find saving graces in each other. Ironically, Chapter 69 in the Boruto manga just subverted this arc from their rivalry, ironically making Sasuke a nihilist in the property's most terrifying moment yet.
No matter what, Sasuke couldn't believe Naruto was so pure of heart. It's only when they fought their final battle and lost their hands that he accepted how Naruto considered him a brother. This changed Sasuke, turning him into a Ranger protecting Konoha and knowing fully that Naruto would have his back, even as an outcast. Sadly, Sasuke just doesn't have that hope, optimism and belief for Boruto.
It got reinforced here when he chatted with Boruto, apologizing over not being there when Momoshiki took his body over in the war against Code. Sasuke knows how Kawaki tried to kill Boruto to prevent the alien inside from coming back to the Hidden Leaf, so they ended up discussing new contingency measures. Sadly, Sasuke maintained his stance in the series' scariest moment yet: if Boruto gets taken over again, Sasuke would make sure to kill him without flinching.
The teen was shocked in this chilling chat because he was expecting a new solution after Momoshiki blew the chance to be reborn in his body -- not to mention Boruto is controlling the remaining part of the alien's soul pretty well. Still, Sasuke can't risk it and is adamant he'll do what needs to be done for the sake of the village, not caring if he'll be vilified by Team 7 or all of Konoha.
This could run him into problems with Naruto, who hated seeing Kawaki espousing the same philosophies which aren't Naruto's ninja way. He may have forgiven Kawaki but still, it's clear Naruto is concerned the boy went that far with his son. As such, he and Sasuke may butt heads once more if Momoshiki pops up.
Naruto believes Amado and Katasuke's science teams can cure his boy, but more so, he thinks Boruto will get strong enough to keep the beast at bay. The question is, will Boruto trust himself or let Sasuke cross this line and break the Hokage's heart one more time? Ultimately, Sasuke's pessimistic plan is not a good way of repaying Naruto's faith -- and may incite a civil war if it comes to pass.