Marvel Studios boss Kevin Feige called Elizabeth Olsen's Wanda Maximoff the most powerful Avenger before WandaVision even began. Now, the MCU Disney+ series has ended, and the show's final episode certainly makes a strong argument in favor of this claim.
THE POWER OF CHAOS MAGIC
WandaVision's penultimate episode established Wanda as the legendary "Scarlet Witch". This means she is capable of chaos magic, which is incredibly powerful, and unlike other types of magic, doesn't require incantations in order to perform. "The Series Finale" provides more information on the Scarlet Witch, including a direct comparison to another Marvel superhero.
During the battle between Wanda and Agatha, the latter says to the former, "Your power exceeds that of the Sorcerer Supreme. It's your destiny to destroy the world," in reference to the legend of the Scarlet Witch. The "Sorcerer Supreme" in question is Benedict Cumberbatch's Doctor Strange, who is known to be one of the MCU's most powerful individuals.
Doctor Strange and the Scarlet Witch are both set to appear in the upcoming MCU movie Doctor Strange in the Multiverse of Madness. Another likely nod to this comes in the final post-credits scene of the episode, which sees an astral projection of Olsen's Wanda - a form fans have seen Cumberbatch's Doctor Strange use before - studying the Darkhold book seen earlier in the episode.
MORE MCU MAGIC
It's clear that the MCU is going to focus more on its "magical" side moving forward, as it started to with WandaVision and will seemingly continue with in Doctor Strange In the Multiverse of Madness. A big debate between fans now that WandaVision is over and more is known about the Scarlet Witch's MCU powers is whether she and Doctor Strange will become allies, adversaries, or some combination of both. The former being more powerful could lead to the latter seeking her out...or it could result in a mess he needs to help clean up.
The point Agatha brings up about the Scarlet Witch's "destiny to destroy the world" is interesting as well. This could be part of the legend Wanda works to avoid, as she says later in the episode that she doesn't need Agatha to tell her who she is, appearing to have a desire to determine her own future as evidenced by her studying of the Darkhold at the end of the series.
However, it could very well come back as a bigger part of Wanda's arc moving forward, with her - purposefully or accidentally - destroying the world (or going down that path somehow). There's also the possibility that Westview is the "world" she's destined to destroy, and removing the Hex towards the end of the episode fulfills that prophecy.
All nine episodes of the Elizabeth Olsen-led WandaVision are now available on Disney+, while the Benedict Cumberbatch-starring Doctor Strange in the Multiverse of Madness is due in theaters on March 25, 2022.