She Becomes the Mad Queen
We all know that Daenerys's favorite word is her dragons' trigger phrase, "Dracarys." She's burned more than a few of her enemies and racked up a kill count that puts Arya's list to shame. As the seasons have progressed, her demands for absolute loyalty and her penchant for taking what she wants with fire and blood has drawn concern and reproach from those around her. (Most notably, her decision to tell the Lannister soldiers to "bend the knee or die," leading to the deaths of Randyll and Dickon Tarly.) Her growing paranoia regarding those she holds close, including Tyrion and Varys, can be seen as a sign of her slowly losing her grip. There's a difference between making a show of power and using power to choke out anyone around you. As her campaign for the Iron Throne continues, Daenerys veers towards the latter a little more often.
It isn't crazy to think that Daenerys might be slipping into her father's old habits and will soon earn the moniker of the Mad Queen. Much like her father's fall to Jaime's sword, Daenerys's end could come from someone she looks to for protection, like Jorah, Jon, or even Tyrion.