7. The Flash
It's a sad state of affairs when the biggest show your shared universe ever produced - heck, perhaps the biggest superhero show ever produced for network TV - ends up this low down the list. But as much as I hate to say it, The Flash's final season completely missed the mark, and even though its finale was one of the better episodes of the season, it was still a far cry from the send-off that it should have been.
The irony is that The Flash is the show that had the longest run of all the Arrowverse shows on this list. It had the most amount of time to prepare for its finale too, as the creative team were informed not long after planning on the season began. While it caught some of the creatives off-guard, they made the baffling decision to continue on with season 9 as though it were any old season, delivering a run-of-the-mill sequence of storylines, each limited to four episodes. It left the final season feeling incredibly disjointed, devoid of stakes, and full of meaningless filler episodes.
There were two outstanding episodes in this season. One was the ninth episode which saw the return of Arrow's Oliver Queen, while the other was "A New World, Part One", which kickstarted the show's final storyline. It set the stage for a strong series finale, but due to the lack of time, the focus on underdeveloped supporting characters like Chester, Allegra and Cecile, and a half-baked villain in Cobalt Blue, it just didn't come together.
The Flash had both the backstory and the tools to deliver a phenomenal series finale that would bid farewell to the Arrowverse and its own characters. But the creative team's decision to act like season 9 was just another season robbed fans of that. And, with the exception of those final two minutes, the show's conclusion was a huge disappointment.