From Hydra volunteer to the Scarlet Witch of Multiverse of Madness.
Wanda loses her parents, her brother and Vision, builds a fake town in WandaVision, and then hunts America Chavez in Multiverse of Madness. Here's what happens, why she does it (it's her sons, not Vision), and the debate over how much of it is the Darkhold.
Levels marked "Sourced facts" are checked against the sources listed at the bottom. Levels marked "Fan theory" are interpretation, not confirmed by the films or their makers.
Wanda and her twin Pietro are Sokovian orphans who volunteer for Hydra's experiments with the Mind Stone; they are the only survivors. In Age of Ultron (2015) they first side with Ultron, then join the Avengers, and Pietro dies. In Civil War (2016) she ends up on Steve Rogers' side. In Infinity War (2018) Vision is killed and Wanda is lost in the Blip; she returns for the final battle in Endgame (2019). In WandaVision (2021), after seeing Vision's body being taken apart at S.W.O.R.D., she turns the town of Westview into a sitcom reality with a new Vision and twin sons, Billy and Tommy. In Doctor Strange in the Multiverse of Madness (2022), now the Scarlet Witch and using the Darkhold, she hunts America Chavez to take her power to cross universes and reach a world where she can be with her sons.
At the end of WandaVision, Wanda takes down the Hex, says goodbye to her family and moves to a remote cabin, where she studies the Darkhold to understand her powers and hears her sons calling for help. Wikipedia's Wanda article, summarising Multiverse of Madness, says she is gradually corrupted by the Darkhold. In the film she kills the Earth-838 Illuminati and many sorcerers at Kamar-Taj. When the Earth-838 Billy and Tommy recoil from her in fear, she realises what she has done and brings down Mount Wundagore, destroying every copy of the Darkhold across the multiverse and apparently sacrificing herself.
This part is fan debate. The official summaries say the Darkhold corrupts her. Some fans argue the book only amplified grief and longing that were already there, pointing to WandaVision, where she traps a whole town before she ever reads it. Others felt Multiverse of Madness pushed her too far. Both are opinions about the character; the films don't settle how much of what she does is Wanda and how much is the book.