Season 7 was the main leviathan storyline. Season 6 and 7 is also when Sera Gamble took over as show runner. I consider season 5 to be one of my favorite seasons of TV ever. She wrote the weakest episode of the 4 horsemen storyline, so I kinda knew this wouldnt pan out for her.
Season 6 was aimless, not knowing what the show wanted to be. Season 7 really pissed me off because
That only lasted 5 minutes into season 7 I believe. ugh.
Season 8 is when the show really found its groove again and became consistently good.