[This is a review of the Supergirl season 2 finale. There will be SPOILERS.]

–

When Supergirl season 2 premiered last fall, it was a somewhat different show than fans had watched through season 1. Beyond shifting networks from CBS to The CW, Supergirl also introduced Kara Danvers' Kryptonian cousin Clark Kent aka Superman (Tyler Hoechlin) and bid farewell to season 1 staple Cat Grant (Calista Flockhart). Those changes have rippled throughout season 2, with Supergirl moving farther and farther away from Kara's job at CatCo Magazine, instead focusing on her work with the DEO.

The second season of Supergirl has also focused heavily on the theme of aliens as refugees on Earth, first through the antagonist of Cadmus -- the anti-alien organization led by Lillian Luthor (Brenda Strong) - and now with the Daxam's Queen Rhea (Teri Hatcher), who seeks to conquer Earth and turn it into New Daxam. Last week's episode, 'Resist', saw the return of Cat Grant as Supergirl struggled to destroy Rhea while saving her boyfriend Mon-El and her best friend Lena Luthor from the Daxam queen. The episode ended on a cliffhanger, with the surprising -- and antagonistic -- arrival of Superman.

In this week's season finale of Supergirl, 'Nevertheless, She Persisted' - with a story by Andrew Kreisberg and Jessica Queller, teleplay by Robert Rovner and Caitlin Parrish, and directed by Glen Winter - Kara faces off against Rhea in her last stand. First though, Kara must save Superman from whatever turned him against his cousin. Plus, Cat Grant remains by Supergirl's side to offer the wisdom that only the queen of all media can give.

The Champion of Earth

'Nevertheless, She Persisted' picks up immediately following the cliffhanger of 'Resist', with Supergirl forced to fight Superman. Who, as Rhea explains, has been dosed with silver kryptonite, which makes him believe he's fighting General Zod (Mark Gibbon) when he's actually battling his own cousin. The mind trickery is over-explained through Rhea's dialogue as she carries on, driving the point home to the point of excessiveness. However, once Supergirl and Superman leave the Daxamite ship and take their fight to National City, it packs a greater punch (pun intended). The action sequence is one of the best in Supergirl's entire second season - and perhaps their first season as well. Plus, it has an added emotional element since it consists of Kara being forced to fight her cousin.

Still, the battle between Superman and Supergirl is simply a precursor to the main event, which, as the National City media portrays it, is Supergirl vs Rhea. After winning their fight while Superman was on silver kryptonite - and, according to Clark, while he was at full strength despite being under the influence of kryptonite - Supergirl becomes the champion of Earth. It's a moment that Supergirl has been building toward since its pilot; the show has established unequivocally that not only is the Girl of Steel as powerful and capable as her cousin, she can be even more powerful and capable.

However, the fight between Supergirl and Rhea doesn't play out exactly as the single combat battle Kara expected when she challenged the Daxam queen. They seem to be evenly matched, so Rhea breaks the rules and unleashes the Daxam forces on National City, forcing Mon-El, Superman, Martian Manhunter, and, in a surprise appearance, M'Gann and her like-minded White Martians, to take the fight to the streets. It's quite a grand scale battle for a sequence outside of one of The CW's major crossover episodes, and provides an entertaining and expansive battle for the season finale, giving each of the heroes time to shine. Still, with Earth's heroes woefully outnumbered, it's up to Supergirl to save the day - with a little help from a Luthor.

The Luthor that Saved the World

A secondary arc throughout Supergirl season 2 has been Lena Luthor's relationship with her mother, Lillian, and, to an extent, the Luthor name since it was tarnished by her brother Lex. That relationship made headway in last week's episode when Lillian asked Supergirl for help in rescuing Lena from Rhea, but Lillian still managed to serve her own agenda by abandoning Supergirl and Mon-El on the Daxam ship that was about to be destroyed by the DEO. In 'Nevertheless, She Persisted', Lena confronts her mother about their relationship, forcing Lillian to deal with her reprehensible actions, especially the effect they had on her daughter.

It seems Lillian and Lena are able to move forward after their emotional, if somewhat brief, confrontation. Or, at least, Lillian brings Lena a peace offering in the form of a device from Lex's vault that could defeat Rhea without harming Supergirl or Superman. The device was created to disseminate kryptonite throughout Earth's atmosphere, making the planet inhospitable to Kryptonians. But, since Daxamites are weakened by lead, Lillian proposes Lena reconfigure the device to rid Earth of Rhea and her forces - though it also means Earth would be inhospitable to Mon-El as well.

Lena brings Supergirl in on the plan and though Kara doesn't want to resort to the device - since it would mean giving up her relationship with Mon-El - she tells Lena to make sure the device works as a backup plan. Of course, Rhea doesn't truly accept Kara's challenge in single combat, forcing Supergirl's hand into using the Luthor device. It would have been set off much earlier if Lillian had her way, but Lena has learned not to trust her mother, instead placing the device's remote in Supergirl's hands. The Girl of Steel proves herself as the Earth's champion and does end up using the device to save the world, despite what it costs her on a personal level.

The Aftermath

With Supergirl spending much of 'Nevertheless, She Persisted' working to defeat Rhea, the final act of the season finale allows time for the emotional impact of Kara's choice to be shown - and for the series to set up its third season. In terms of Mon-El's departure, it's truly the perfect emotional capstone to their season-long arc as a couple as well as the Daxam prince's evolution into a hero and Kara's into the selfless champion of Earth. Prior to their final scenes together, the episode took the time to showcase Kara and Mon-El at their happiest - albeit in a dream sequence - which makes their farewell that much more heartbreaking.

Still, Kara has a wealth of close friends and family who are there to support her, whether it's her cousin Clark or her sister Alex. However, no motivational speech can match that of Cat Grant, as Calista Flockhart proves once again how integral her dynamic with Melissa Benoist's Kara is to the heart of this series. Certainly, Supergirl has maintained its heart in season 2 without Cat, but it isn't quite the same. It's incredibly refreshing to see such a positive female-centric mentor-mentee relationship on television, one in which there aren't really any secrets as Cat reveals - albeit only to the audience - that she knows Kara is Supergirl.

While these emotional scenes add balance to 'Nevertheless, She Persisted', the final minutes of the episode work to set up next season. A mysterious wormhole swallows up the pod in which Mon-El fled from Earth and a flashback sequence is shown to the day Krypton was destroyed. In it, a baby is placed in a Kryptonian pod and sent to Earth. Who - or what - that baby grew up to be will no doubt be a major through line in season 3. After an excellent second season, Supergirl sets the stage for another intriguing mystery that will hopefully help the series continue to build on the character-driven DC Comics adaptation.

Next: How Movie & TV Representation Saves Lives

Supergirl returns for season 3 this fall on The CW.