Knowing Game of Thrones, the valonqar theory may not be the only element to play into Cersei's downfall. Just about everyone in Westeros would love to see the Queen's head on the chopping block, and that's what makes this next theory so compelling. Reddit user MahatmaGuru believes that Gregor Clegane, the Mountain, will turn on Cersei at a moment when she threatens his creator Qyburn. Though this prediction is tough to swallow, there's room for such a fallout between the pair since Cersei has isolated herself from everyone and appears to grow more paranoid and self-protective with every episode.
Even if Qyburn turns his monstrous creation on Cersei in self-defence, an escape may be possible, leaving her vulnerable to attack from others such as Jaime or the Night King. Or perhaps, the Night King takes control of the Mountain, who is technically a reanimated corpse, and tasks the brute with killing everyone in the Red Keep. Just think what a badass the army of the dead would be with a dragon and a Clegane on their side.