WARNING: The following contains spoilers for Eternals, now in theaters.
Chloé Zhao's Eternals has finally premiered in theatres to mixed reviews, with critics calling it an ambitious but overstuffed addition to the Marvel Cinematic Universe. Some of this criticism has been directed toward the film's handling of Kro and the Deviants, a race of alien lifeforms created by the Celestial Arishem to wipe out predators stalling evolution that eventually grew into predators themselves.
Arishem then created the Eternals to wipe out the Deviants throughout the universe, which led to them arriving on Earth. While the Deviants were initially presented as threats to humanity's existence and enemies to the Eternals, they were later pushed aside when it was revealed that Arishem and the Eternal, Ikaris, planned to destroy the Earth with the Emergence of a new Celestial, Tiamut. Eternals thus disregards and mishandles the Deviants, as they are an essential part of the Eternals' story that could've been improved on significantly.
Though the Eternals on Earth thought they had already killed all the Deviants, Ikaris discovered that a few more Deviants, including Kro, were frozen in Alaska and thawed out due to global warming. Betraying his fellow Eternals to fulfill Arishem's goal, Ikaris throws Ajak to them, allowing them to gain her healing powers and some degree of sentience. After killing and absorbing Gilgamesh, Kro finally becomes fully self-aware, learning the history of the Celestials and the Eternals, which fills him with hatred and a thirst for vengeance towards them all.
However, Kro should've become fully self-aware once he absorbed Ajak's power and knowledge, as it could've made him both a much more threatening enemy to the Eternals and an actual character instead of a force of nature. It could've also given the film more opportunities to explore his character, showing more of how he was motivated by revenge against Arishem and the Eternals, as well as a desire to protect his kind. His intelligence alone could've made the Eternals question whether or not they should kill a being who's self-aware.
While Kro and the Deviants' presence raises ethical and philosophical questions, with the Eternals acknowledging they were both pawns in Arishem's design, they don't appear to have a bigger role in the plot other than to battle the Eternals in a few Hollywood fight scenes. After the heroes learn about the Emergence, the Deviants don't best serve as Eternals' antagonists because, unlike Ikaris, they aren't actually trying to prevent them from achieving their goal. They just want to kill the Eternals because they tried to do the same to them in the past.
If Kro did become sentient early on in Eternals, Kro and the Deviants could've tried to kill the Eternals to prevent the Emergence and preserve their existence, having learned Arishem's true goal after absorbing Ajak's knowledge. Thus, Sersi and the others could've learned about the Emergence later in the story, making the return of the Deviants the true reason they all reunite. Kro could've hinted the truth about the heroes' purpose on Earth to make them question their mission before Sersi learned it directly from Arishem.
Kro's hatred of the Celestials and the Eternals ultimately conflicts with his actions during the film's final battle, which he joins from out of nowhere after a lengthy absence. Though Ikaris intends to allow the Emergence of Tiamut to go through and destroy the Earth, Kro actually helps him by fighting against the other Eternals until he is killed by Thena. While this may not have been intentional on Kro's part, his actions protect the man fighting for the Celestials, whose plan threatens his and the rest of his kind's fate.
To make Kro a more well-rounded character, he should've teamed up with Sersi and her team to stop the Emergence. Despite how the Eternals wiped out the rest of his kind, the Deviant should've pushed his hatred towards them aside and joined with them in defying the Celestials and trying to save his kind and the planet. Just as the Eternals asserted humanity's right to exist, so should Kro have asserted the same right for the Deviants.
Though this would've made for a more satisfying arc for Kro, this revision wouldn't completely work without addressing the fact that he murdered Gilgamesh during their battle in the jungle. Thena would've had a difficult time teaming up with the one who murdered her long-time companion, and it wouldn't have felt right if she just decided to team up with him after that. For this reason, Ikaris could've been the one who murdered Gilgamesh, possibly after the latter tried to stop his plan, as it would make it easier for Thena to ally with the Deviant.
In the end, after Sersi turned Tiamut's body into marble and saved Earth, Kro and the surviving Deviants, if any, could've made a truce with the Eternals and settled on the Celestial's gigantic corpse, where they could live in peace without harming any more humans. This wouldn't be the first time that people in the MCU have made homes out of a Celestial, as Guardians of the Galaxy displayed with Knowhere, a settlement made out of a Celestial's severed head.
While Eternals is a beautiful, heartful and thought-provoking film, Kro and the Deviants can't help but seem like a missed opportunity that got in the way of the story's real conflict within the titular team. In a massive blockbuster filled with a variety of characters with complex backstories, the Deviants ultimately ended up as an afterthought in the grand scheme of things when they deserved so much better.
To see how Kro and the Deviants are ultimately sidelined, Eternals is now playing in theaters.