9. Cul Borson
After two movies of being told that Thor and Loki were Odin’s only two children, Ragnarok dropped the revelation that he had been hiding his first born Hela, the Goddess of Death. If Thor can have an estranged MCU sister, what about an estranged uncle?
Cul Borson is the brother of Odin in the comics, and the much hated God of Fear. During Jason Aaron’s Thor, Cul is brought in by the Allfather to control the Destroyer, with the goal of taking Mjolnir back from the mysterious woman who had taken the Odinson's weapon and name.
It was Odin who was deadly set against the new Goddess of Thunder, and did everything he could to find out her identity and take his son’s weapon back. He felt embarrassed, ashamed, and insulted. However of course, Odin is no longer a part of the MCU, so this role could be taken entirely by Cul.
If Odin exiled his daughter, he could well have exiled his own brother too. Depending on just exactly how much inspiration the movie takes from the source material, the God of Fear could return to try and retrieve Mjolnir and the title of Thor for his nephew, and for Asgard.