Catra Ruins Everything

Metaphysical / Paranormal event

The Events of S3E5-6 a lot happens.

Because of Adora's prompting, Entrapta reexamines the models and realizes that even with the sword, the portal could prove horribly destructive. Because Entrapta is erring on the side of safety, Catra knocks her unconscious and has her goons ship Entrapta to Beast Island. Because Catra is determined to see this portal thing through to the end, she activates it against Adora's warnings.
The portal causes reality to collapse in on itself. Everybody begins experiencing alternate-timeline versions of their lives. Adora realizes that something is wrong and asks Catra to help her fix it.
  Catra: "I won't let you win. Id' rather see the whole world destroyed than let that happen."
  Because of repeatedly having her desires thwarted, her ambition stifled, and everything she's ever cared about destroyed or taken from her, Catra begins to despise the good for being the good. She almost certainly doesn't think of it in those terms, she's probably hating Adora because she doesn't understand why Adora is achieving success while she isn't. Because she has given in to her hatred of Adora, Catra refuses to help Adora fix the collapse of time and space. She actively resists this process.
Because Adora encounter Madame Razz, she learns that Mara saved the world rather than destroy it as Light Hope claims. After reuniting with Bow and Glimmer, and consulting with Entrapta, Adora realizes that she has to interact with the portal itself, and to do that she needs to go and find it. She does so and encounters Catra. Catra appears to have been partial eaten by the disintegration of time and space.
Catra makes a fallacious argument as to why everything that has happened is Adora's fault.
Adora rebukes Catra and says that she is not responsible for Catra's decisions and actions. She tells Catra that she's made her choice and will now have to live with it. Adora punches Catra into the void.
Angela appears to Adora, summarizes her character arc, and then traps herself in the space between the openings of the portal in order to close it.