Warning: Spoilers for The Flash season 8, episode 20
Barry Allen’s dilemma about killing Reverse-Flash needs to be laid to rest after The Flash season 8. Supposedly, Tom Cavanagh’s Eobard Thawne has been defeated for good. But though the episode ended with the impression that their troubles with Reverse-Flash are over, that hardly means anything where this particular character is concerned.
In The Flash season 8, episode 20, titled “Negative One”, Grant Gustin’s Barry Allen engaged in what was presented as his final showdown with his greatest enemy in the Arrowverse. With Barry and Thawne powered by the Positive and Negative Forces respectively, the two were able to fight it out all over the Central City in a no-holds-barred brawl. But instead of fighting it out until one of them died, Barry refused to continue after finding out that Iris was still alive, which resulted in Thawne incidentally destroying himself with an overload of his Negative energies. In other words, it was ultimately Barry’s refusal to finish Thawne off that caused his defeat.
Of course, it took most of the episode for Barry to reach a point where he no lingered deemed it necessary to kill Cavanagh's Eobard Thawne. While Barry has a well-known no-killing rule in the Arrowverse, his inner conflict over Reverse-Flash’s fate was not an unfamiliar struggle for the character. In fact, it’s one that’s gotten really old. After all, this isn’t the first time that Barry has deliberated over killing Thawne while also facing opposition from his teammates over his reasoning. The Flash already did this story once in season 8 (“Armageddon, Part 5”) so there really wasn’t a need for the show to do it all over again.
A big part of what makes this recurring debate such a tiring storyline for The Flash is the fact that it hasn’t changed. Each time The Flash goes down this road with the Reverse-Flash or any other Arrowverse villain, the resolution is the same, thus making the ending predictable. No matter how angry he is, Barry will never willingly take a life. Even if he wants to kill Reverse-Flash or just let him die, someone else in the show will be there to talk him out of it. Even though Iris’ “death” gave Barry more incentive than ever to go through it, there was very little expectation that Barry would go through it, especially since Iris’ scenes with Neal McDonough’s Damien Darhk confirmed she wasn’t dead.
The show has exhausted its use of the debate over whether or not Barry should break his biggest rule for Reverse-Flash, which is why the show should find ways around it if he comes back in The Flash season 9. Thawne may be dead now, but all the other times he’s died in the Arrowverse prove that what happened in the finale won’t stand in the way of his character returning in the future. Hopefully, whatever scheme he’ll be up to if and when he re-enters the picture won’t involve yet another repeat of season 8’s Reverse-Flash drama.