With WandaVision and Doctor Strange: in the Multiverse of Madness on the MCU horizon, the Scarlet Witch is set to have a more pertinent on-screen presence than ever before, with all signs pointing to House of M as the blueprint for Wanda's upcoming character arc. House of M famously displayed the extent of Wanda's reality-altering powers as a consequence of her unhinged mental state, but the lesser-known narrative prelude to that storyline, Avengers: Disassembled, featured a bone-chilling twist far too disturbing to be featured in anything under the Disney banner.
Avengers: Disassembled by Brian Michael Bendis and David Finch is essentially a disaster movie starring the Avengers as victims to forces beyond their understanding. The storyline begins at breakneck speed as the Avengers are attacked at their headquarters, leading to the deaths of team members Vision, Ant-Man, and Hawkeye. With no understanding of who's behind their greatest defeat ever, Doctor Strange arrives to inform the Avengers that it was their own teammate, Scarlet Witch whose psychotic break subconsciously orchestrated the attack.
The story creates an overwhelming sense of dread as layers are methodically pulled back to reveal the extent of Wanda's mental deterioration. It's one thing to discover the Scarlet Witch lost her mind and destroyed the Avengers, but when her teammates find her holed up in an empty house, having dinner with a family she created from her own delusions, it becomes increasingly more apparent that Wanda's been fully consumed by her illness. And it only gets worse. After Doctor Strange defeats Scarlet Witch and puts an end to her reality manipulations, Nick Fury investigates Wanda's vacant home to discover the rotting corpse of an old woman propped up and sitting on a chair in the middle of a darkened room.
It turns out this victim is none other than Agatha Harkness, Wanda's longtime witch mentor who guided her in the use of her powers on more than several occasions. In a storyline chock-full of shocking revelations, this one may be the most horrific of all due to its subtle implications. Wanda killed one of the most powerful sorceresses on earth off-panel, and in the midst of a devastating mental breakdown. And Fury's discovery of Agatha's dead body is a clear homage to Alfred Hitchcock's Psycho in the scene where it's revealed Norman Bates was having delusional conversations with the decaying remains of his mother all along. Imagining Wanda had spent all this time alone in an empty house, speaking to her deceased mentor's carcass drives home the frightening levels of insanity she reached without her fellow Avengers even knowing it.
With Kathryn Hahn all but confirmed to portray Agatha Harkness in WandaVision, the elder witch's death at the hand of her greatest student could very well be included in an upcoming Marvel Studios project, just don't expect it to be executed in as graphically disturbing a manner as it was in the comics. The House of Mouse simply wouldn't risk inducing such a high level of terror in their audience. Still, this moment will forever be engraved in comic book history as the moment the Scarlet Witch was revealed to be a deranged killer comparable to the likes of Norman Bates.