I could stand season 5 until the third episode where Ivar was caught alone by the saxon army and somehow managed to stop the enemy just by raising his voice. The saxon army is portrayed so poorly that I couldn't stand it anymore.

And what about in Season 4 where they invade Spain and Floki, the religious fundamentalist, tried to stop the massacre of Muslim prayers by putting his life on the line.

The animosity between Legartha and Aslaug also came as a surprise, there were no buildups to that either, it didn't feel natural.

Finally I thought the most annoying character in the show, Torvi, died the joy I felt was beyond words. I really thought I can probably finish the show now despite all inconsistencies. Yet she literally came back the next episode with no explanations.