While fans posit that Boruto anime’s opening moments show us the series’ final battle, there are better theories based on the story so far.
The Boruto anime opens by giving viewers a look at adult Boruto vs adult Kawaki, with a ruined Hidden Leaf their battleground. However, as a presumed parallel to Naruto Shippuden, this is likely a battle between rivals rather than our hero vs. the final villain.
The identity of the final villain in Boruto remains a mystery
Much like in Naruto, Boruto gives our eponymous protagonist a friendly rival in the form of Kawaki. Their relationship was distant at first, but much like Naruto and Sasuke they bonded through training and shared missions.
The Uzumaki family canonically views Kawaki as another son, further emphasizing his and Boruto’s brotherly nature.
Kawaki and Boruto also find themselves possessed by the Otsutsuki Karma, a means of reincarnation and revival for the heavenly shinobi clan. It’s similar to Orochimaru’s reincarnation jutsu, but wireless, for lack of a better term.
This parallels how Sasuke was figuratively possessed by the Uchiha burden of love, and Naruto literally by Kurama.
With Kishimoto having taken over the manga as of the manga debut of Baryon Mode, the Naruto parallel Boruto has already given us will expectedly become more frequent. Going off this assumption, there’s a very safe assumption that an Otsutsuki will be Boruto’s final villain.
The Otsutsuki Matriarch's return?
Kaguya is a safe bet, generally speaking any Otsutsuki could fit the role of the final villain well enough to parallel Naruto. Kaguya would add to the symbolic parallelism by showing Boruto and friends are just as strong as prime Sasuke, Naruto, and Sakura.
However, the favorite would likely be Isshiki Otsutsuki via reincarnation through Kawaki. He’s already been presented as a dangerous force in Boruto who essentially required Kurama’s sacrifice to beat.
Isshiki’s Karma on Kawaki has already proved to be unstable, something which merits concern after seeing Momoshiki take control of Boruto.
Isshiki also has somewhat of a backup plan in the form of Code. While Code was unsuccessful in becoming Isshiki’s chosen vessel, he did still receive a Karma. This Karma is what allowed Isshiki to communicate with him, similar to Momoshiki communicating with Boruto.
Code may seem the most likely candidate, but the task ahead of him is too great and the claim refutable thanks to Boruto’s opening scenes. While definitely shaping up to be a significant villain for Boruto and Kawaki’s journey, he doesn’t currently feel big enough for final villain status.
The question of who will be the final villain in Boruto is one fans have asked since the series' opening scenes.
While still undetermined as of this writing, there are very clearly some likely candidates in the form of the Otsutsuki clan at large. After all, they’re responsible for most plot development so far, which shows no signs of slowing down.
While some Otsutsukis would fit the role better than others for various reasons, they are the safe bet at large right now. Boruto’s intent to parallel Naruto has been obvious so far, and to not have Boruto, Sarada, and Kawaki take on an Otsutsuki would be a missed opportunity.