7. Season 6A
Although Season 6A is an improvement over the preceding season, it introduces far too many new characters for a show in its penultimate season. These all stem either from Bjorn's journey to become King of Norway or Ivar's exile. Although we finally see King Harald reveal his true intentions to beat Bjorn to the crown, the introduction of the various Kings, Jarls and Earls, and the power dynamics between them during the moot, falls flat as they only exist to serve the plot at this point.
The Russia storyline with Ivar suffers from this problem, as well. The introduction of the Russian dynasty and the scheming between Prince Oleg and his brothers feels irrelevant at this point in the show. Despite being placed in this scenario, Ivar's goals and motivations are much better in this season. The viewer can see Ivar suffering, beginning to understand the error of his ways. He genuinely cares for Igor, and the paternal guilt he feels for leaving his son Baldur to die of exposure plays a large part in this.
Removed from the squabbling of Kings is Lagertha, who has a much smaller scale story to reflect her twilight years. Just as she thinks she has left the Shieldmaiden life behind, she is drawn back in for one last conflict. However, Lagertha's death lacks the impact and scope it truly deserved, which feels criminal for a character of her calibre.
When all is said and done, Lagertha did not really die for anything other than to further Hvitserk’s arc.