The MCU's next superhero, Black Knight, will make his debut in Eternals - and in the comics he's actually more powerful than Thor. The Marvel Cinematic Universe continues to grow, and in 2021 viewers will be introduced to heroes like Shang-Chi, the Eternals, and the Black Knight. In the comics, Dane Whitman is a scientist who was thrust into a world of sword-and-sorcery superheroics when he learned that he had inherited the cursed Ebony Blade from his ancestor, Sir Percy of Scandia. The MCU version of the Black Knight will be played by Kit Harington, and his precise role in Eternals is unclear.
The Black Knight is an unlikely addition to the MCU. He's not exactly an A-list superhero; although he was an Avenger for a time, that was a period where the Avengers were second- (or probably third-) stringers in sales terms next to the X-Men and Spider-Man. The rest of the Avengers have historically treated the Black Knight with a degree of disdain, disturbed by his habit of narrating to himself in a fake Olde English accent as a coping mechanism to attempt to rein in the Ebony Blade's dark influence. Yet, for all that's the case, recent comics have retconned that the Black Knight is actually more powerful than Thor himself.
Thor may have Mjolnir, but Dane Whitman has the Ebony Blade. This weapon was forged from a meteorite by the sorcerer Merlin, and its true nature is something of a mystery; Knull, the God of the Symbiotes, taunted the Black Knight that he has no idea how powerful it truly is. He hinted that the Ebony Blade had the power to crack the world itself, and the Black Knight: Curse of the Ebony Blade miniseries - written by Si Spurrier, with art by Sergio Fernandez Davila - has revealed how. It seems the Ebony Blade is the antithesis to Mjolnir, in that it "lightens only in shadow." The more unworthy the person who wields the Ebony Blade, the more powerful it becomes. When Dane Whitman meditates upon his own inner darkness, his wounded pride and vanity, the Ebony Blade becomes a WMD.
The striking thing is that this makes the Black Knight more powerful than Thor himself. Black Knight: Curse of the Ebony Blade #3 featured a flashback to the days of ancient Camelot, when Thor Odinson led a group of Viking raiders in an attack upon the city. Black Knight stood in its defense, and Thor couldn't resist taunting him as he battled Arthur's champion. He had no way of knowing that Black Knight became ever more powerful as Thor undermined his confidence and fueled his self-hatred until finally, the Ebony Blade erupted in a flare of cosmic power. One blast was enough to knock the Odinson out. Ironically, Thor can count himself lucky he wasn't killed; the Ebony Blade consumes the souls of its victims, so this could have been the end of the Thunder God.
This is how powerful Black Knight truly is in the comics, and it will be fascinating to see how he is handled in the MCU. All these retcons have been brought into place over the last year, since Marvel Studios president Kevin Feige was appointed Chief Creative Officer of Marvel Entertainment, giving him creative oversight over the comics. That means it's entirely possible Black Knight's powers have been amplified in the comics ahead of Eternals - in which case, Dane Whitman could be one of the MCU's greatest powerhouses to date, easily surpassing Thor.