Oh my god, I'm going to have to rewatch all of Agatha All Along now because so many things just fell into place. First, Rio mentions how Billy disrupts the "sacred balance" because he got another chance at life by jumping into William Kaplan's body. The "sacred balance" of things is also something Thanos consistently talked about when wanting to get rid of half of all living things. When Agatha and Rio, aka Death, come face-to-face, she mentions that Agatha is walking a road with "another woman'