When adapting comic books, one should always expect a multitude of changes, some of which are beneficial, but many of which are detrimental. Unfortunately, Craig Gillespie's Supergirl, starring Millie Alcock, is another example of these changes for the worse, one of which completely undermines the thematic foundation of Supergirl: Woman of Tomorrow, written by Tom King and artist Bilquis Eveleigh.
Even then, the news that DC Studios co-CEO James Gunn had hinted that Supergirl's origins were set before, rather than after, Crisis was cause for concern. This change was confirmed by Kara herself in the Supergirl series, when she told Ruthie her tragic origin story, mentioning that she was born eight years after Krypton's destruction and raised on the remains of Argo City. But even this change pales in comparison to the ending.
In the original comic, after Kara and Ruthie finally captured Cream in hopes of extracting the antidote for Krypto, Ruthie was left alone with him when Supergirl had to fight the Rogues. The young woman seized this as an opportunity to finally get revenge on Cream for killing her father, even putting up a decent fight and easily defeating him. But when the moment came to kill Cream, Ruthie couldn't bring herself to do it.
However, Supergirl soon returned with the body of Comet, Kara's Kryptonian horse (long story), who had died helping her fight the bandits. Utterly distraught, Supergirl was ready to kill Krypto herself until Ruthie tried to stop her, as there was no antidote for Krypto yet. This is where the major plot twist of Supergirl: Woman of Tomorrow is revealed: Krypto was fine, and Kara lied.
Poison had never been dangerous to the dog, and she'd known what Cream looked like from the start. She'd used both as excuses to embark on this journey with Ruthie and try to teach her a simple lesson: killing is wrong, but more importantly, it won't bring her true closure.
As Kara prepared to swing Rutee's family sword to sever Cream's head, the girl desperately screamed at the Kryptonian that she had learned her lesson. That after everything she had seen and experienced during their journey together, she understood:« "Enough killing already.". Kara relented, sparing Cream and instead imprisoning him in the Phantom Zone as punishment.
The fact that Supergirl is portrayed as pre-Crisis rather than post-Crisis, while regrettable, isn't a deciding factor. The poison's real danger to Krypto is another change that diminishes character depth but gives viewers a more personal goal for Millie Alcock's Kara to pursue. Jason Momoa's appearance as Lobo, while not essential to the film's plot, doesn't detract from it.
What really ruins it is the ending, which contradicts not only its own themes but also its source of inspiration, Supergirl: Woman of Tomorrow—a straightforward deconstruction of the typical desire for revenge and the emptiness that comes with retribution.
How the DC Universe Ruined the Ending of 'Woman of Tomorrow'«
The climax of the Supergirl series culminates in a massive battle with the Rogues and Cream, the latter of whom Supergirl, having recovered from the planet's cryoponite sun, brutally beats. Ruthie holds him at her mercy, wielding her father's sword, ready to kill, but, unlike in the original comics, it's Kara who has to convince Ruthie to stop. Again, a minor change that achieves the same result: Ruthie learns the lesson that killing Cream will only destroy her soul.
They embrace, Kara takes the sword from Ruthie, and immediately negates the film's entire moral premise by vengefully plunging Ruthie's family sword into Cream's stomach and then into his throat, killing him. Yes, Supergirl does this in the name of all the countless women Cream trafficked and her dog, but it still distorts the core lesson of the film itself, not to mention the comic book it's based on.
If Supergirl had presented this as something that would negatively impact Kara, as she warned Ruthie, it would have made more thematic sense, as Kara's way of saving the girl's still-innocent soul. Instead, the film presents it as the morally correct decision, and by the time Kara returns to Earth, she appears happier and more confident, setting the stage for her next appearance in the sequel with her cousin.
It's not that Kara Zor-El is entirely opposed to murder or the death penalty. This is explicitly stated in the fifth issue of Supergirl: Woman of Tomorrow, when she and Ruthie witness the public execution of one of the outlaws at the hands of the inhabitants of the planet he helped plunder and destroy, and Supergirl does nothing to stop them.
A more appropriate scenario, given the film's themes and Kara's insistence to Ruthie that killing Cream won't bring her relief, would have been for Cream to be killed by women enslaved by the Rogues, with Supergirl deliberately not intervening. This would also evoke the film "Supergirl: Woman of Tomorrow," where the inhabitants of that planet kill a Rogue.
In Tom King and Bilquis Evele's Woman of Tomorrow, Kara sought to change the mind of just one girl, not the entire galaxy. But the film seemed to emphasize the moral superiority of murder while simultaneously providing the ultimate satisfaction of seeing the hero kill the villain.