Warning: Spoilers for The Flash season 9, episode 10

It took eight years, but The Flash has finally justified Reverse-Flash’s return. The CW series famously killed off the character known as Barry’s greatest enemy in the season 1 finale, yet that was hardly the end of his story. The character has made a multitude of appearances since his original defeat.

Through plot devices like time travel, The Flash has found numerous ways to bring Eobard Thawne back into Barry’s orbit. It didn’t take long for it to become apparent that Eddie’s death – which resulted in Reverse-Flash being erased from existence – didn’t have the long-term impact that was originally implied from the season 1 finale. Barry has had to deal with Reverse-Flash so many times since then that Eddie’s sacrifice in The Flash felt rather pointless. In addition to the times Barry has had to face earlier incarnations of his season 1 villain, he’s also engaged in new conflicts with Reverse-Flash, beginning with season 5.

The Flash Season 9 Proved Why Reverse-Flash Had To Return

Legends of Tomorrow Reverse Flash Eobard Thawne fading away in time

At last, the series has validated its decision to bring back the Reverse-Flash after season 1. In The Flash season 9, episode 10, titled “A New World, Part One,” Thawne deviously arranged for a time-displaced Barry to spend a day with his parents right before the tragic event that shaped his life. To Thawne’s disappointment, his plan allowed Barry to make peace with what happened, as the day served as a touching reminder of his parents’ love. The loss of his parents has always been a crucial element of Barry’s story, and one that hinged on Reverse-Flash’s involvement, hence why Thawne needed to remain relevant to the series.

Understandably, the death of Barry’s mother and his father’s wrongful incarceration weren’t events that The Flash simply moved on from after season 1. These events shaped Barry’s early life, so it made sense for his tragic backstory to be important to every season. Reverse-Flash was the catalyst for all of it, so in turn, using him as a recurring foe kept that theme alive in The Flash. And for that story to properly end, the conclusion naturally had to incorporate Reverse-Flash. Barry thanking Thawne and effectively ruining the villain’s most cherished moment was an appropriate ending to their rivalry and the story as a whole.

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Reverse-Flash’s Perfect Ending Couldn’t Have Happened In Season 1

Matt Letscher as Reverse Flash in The Flash Show

The closure found in The Flash season 9, episode 10 most likely wouldn’t have worked at an earlier point in the series, much less before Reverse-Flash’s death in season 1. Given that Barry hadn’t created Flashpoint yet to undo his mother’s death, the series was a long way away from this development. Barry's expression of gratitude to his archenemy was not a moment that he could have reached in a single episode; it was a journey that actually took years of character growth. Ultimately, only season 9’s Barry Allen, a character who has nearly arrived at the end of his Arrowverse arc, could have pulled off this scene.