It appears that in every past season of Game of Thrones, exactly once, a king dies:
1. Robert Baratheon (S1E7)
2. Renly Baratheon (S2E5)
3. Robb Stark (S3E9)
4. Joffrey Baratheon (S4E2)
5. Stannis Baratheon (S5E10)
6. Tommen Baratheon (S6E10)
Now that the Season 7 is over, by going over the episodes, I do not remember this happening to a king. Of course the definition of "king" is highly debatable: everyone can claim to be one, but we know that power resides where men believe it resides.
So maybe I am simply not looking at things from the right angle. For instance, a possible exception is that in Season 1
Viserys Targaryen dies (S1E6).
Has an event of this kind happened in Season 7 as well?
Bonus question: Was this a coincidence in the past seasons, or are there indications that it was planned along by the writers/author?