WARNING: The following contains spoilers for The Eternals, now playing in theaters.
The Eternals are among the most powerful beings in the Marvel Universe. Created by the Celestials, the cosmic race has reserves of power that make them among the more potentially devastating individuals in the entire universe, but even they have their limits.
Eros, aka Starfox, has just made his big-screen debut -- but the character's comic book counterpart wasn't nearly as powerful as he believed, with his ability to control emotions failing miserably against an enraged Hulk.
Starfox -- the brother of Thanos -- made his Marvel Cinematic Universe debut in the post-credits sequence of Eternals. Played by Harry Styles, Eros is introduced as a charming Eternal who wants to help Thena (Angelina Jolie) and her companions find the rest of the Eternals across the cosmos. In the core Marvel Universe, Starfox instead became a major Avenger for a time before returning to the cosmos until he ultimately perished in a failed attempt to revive Thanos. Eros' abilities grant him enhanced strength, speed, and durability. His most useful (and potentially sleazy) ability however is his control over emotions. He's used this to calm enemies and crowds in the past, and it's an ability that became more controversial following a She-Hulk story arc that focuses on him.
Starfox's encounter with She-Hulk's famous cousin didn't go well for him, however. After trying to turn the Hulk into a more overt hero and working with SHIELD, Bruce Banner was targeted by Nightmare and once again lost control of the Jade Giant. Going on a rampage, the Hulk made his way across the country, blowing through all resistance and eventually ending up in New York City. There, the Hulk faced off with a plethora of heroes in Incredible Hulk #300 (by Bill Mantlo, Sal Buscema, and Gerry Talaoc). Completely untethered from the restraints of Banner's mind, the Hulk proves nearly unstoppable in the ensuing conflict, shrugging off the efforts of Human Torch, Iron Fist, and Luke Cage.
This prompts the Avengers to arrive on the scene. At the time, the roster consisted of Thor, Vision, Scarlet Witch, Photon (during her days as Captain Marvel), and Starfox. In an attempt to end the fight quickly and easily, Starfox decided to try and "tame the beast" by controlling the Hulk's emotions. Using his emotion manipulation abilities, Eros attempted to transform all the Hulk's rage into pleasure and ecstasy. But the Hulk proves to be so angry at that moment that Starfox's attempt is useless, and he is rewarded with a powerful punch that sends him flying, surviving due to his Titan physiology. Ultimately, not even Thor can defeat the fully untethered Hulk, forcing Doctor Strange to banish the Hulk to the extradimensional region called the Crossroads where he can no longer hurt the people of Earth.
While Eros has a slew of impressive powers, he's also not nearly as powerful as he believes himself to be. Even his abilities have their limits, and the only reason he survived his encounter with the Hulk was because of his innate strength. While his debut in the MCU might set up a new showcase for the character and his abilities, it's worth remembering that Starfox does have his limits, especially when his greatest ability is rendered useless.