The WandaVision Scene That Went Too Far
When "WandaVision" first starts, it's easy to get fooled into thinking the series is just going to be a goofy little MCU spin-off parodying the sitcoms of old. Everything seems benign enough, from the silly premise to the procedural plot about Wanda (Elizabeth Olsen) and Vision (Paul Bettany) hosting an impromptu dinner party. By the end of the first episode, however, it becomes clear that not everything is as it seems.
By the end of the series, we know that the sitcom schtick is just a facade created by Wanda to cope with her grief. After losing everyone she ever loved, Wanda went haywire and used her powers to create an ideal life (based on her favorite sitcoms) in the humble town of Westview, New Jersey. Unfortunately, this process entails brainwashing an entire town to constantly do her bidding, something that also locks her victims in a state of perpetual mental torment. It's actually quite a dark turn of events in contrast to the show's seemingly lighthearted premise.
Among all of that, however, there is one "WandaVision" scene that almost went too far in how dark it gets. It occurs during Episode 6, "All-New Halloween Spooktacular!," after a sudden turn of events causes Wanda to go off the deep end once more. What she does afterward is so dark that it's actually kind of disturbing.
When Wanda doubles down on evil
We'll admit, this answer is almost a bit of a cop-out because the disturbing action in question is something that Wanda does for the entirety of the series. The problem is that there's really no two ways about it — brainwashing the entire population of a town is about as bad as you can get without breaching into Thanos territory. What makes Wanda's behavior worse in this scene, in which she attacks the fake Pietro (Evan Peters) and further expands the borders of Westview, is that she is completely conscious of her actions and their implications.
When Wanda first alters Westview, you could argue that it's something she does unconsciously, or at least represses the memory of doing so. Her moral senses urge her to lie to herself. By the time Episode 6 rolls around, however, Wanda is fully aware of what she is doing. At first, the problem seemed to be contained, with Wanda content not to cause any more damage as long as SWORD kept their space. But when Vision discovers the borders of her illusion spell and tries to break free, Wanda snaps again.
Not only does she attack her long-dead "brother," but she also expands her Westview spell even further, enslaving more people and doing more damage. But she doesn't care as long as she gets to keep her family. It's one of the most harrowing moments in the show because audiences finally see how far gone Wanda is.