Which was the worst season?
I think the final season was the worst.
It lacked the intensity of the other seasons.
The characters were less intense, as if they'd lost motivation somewhat.
The events were less interesting, even the cancer didn't seem as big as earlier events.
I think the earlier seasons did a great job of making seemingly minor events into epic moments.
It was like someone different was directing the final season, or maybe they just lost their passion.
Also I think there were too many characters in the final season, so there was less screen time to focus on what/who mattered most.