You have to admire the chutzpah of Supergirl's writers and their choice to name the Season 4 finale in honor of what is widely regarded as the worst Superman movie of all time: "The Quest for Peace." But it's not so crazy when you consider how much Superman IV and Supergirl: Season 4 have in common. Both are steeped in political allegory about tensions between East and West. Both feature Lex Luthor trying to destroy one Kryptonian hero by harnessing their evil doppelgänger. Both are concerned with the need to achieve peace in our time. It's just that Supergirl is much better about actually realizing those lofty ambitions.

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Without burying the lede, Season 4 is easily Supergirl's strongest to date; that much has actually been obvious for quite a while. While this season made some improvements to the supporting cast and other areas, it succeeded by turning what has historically been the show's most glaring weakness into its greatest strength.Prior to this season, Supergirl has never had a villain worthy of rivaling Kara Danvers. Not Maxwell Lord. Not Lillian Luthor. Not the Daxamites. Nobody. But Season 4 flipped the script by giving fans an embarrassment of riches. The season opened with the introduction of Agent Liberty/Ben Lockwood (Sam Witwer), a character who probably could have shouldered the burden all on his own. It helps that the show wasted so little time before delving into Lockwood's tragic past and showing how even decent men can be transformed into hate-mongering bigots if pushed far enough.But Lockwood was just the start of Season 4's salvo. Even as the series worked to establish a new mission and purpose for ex-DEO head J'onn J'onzz (David Harewood), it also gave him a new antagonist in Manchester Black (David Ajala). That wrinkle is one of the more memorable twists to the source material in Season 4. In the comics, Manchester is a Superman villain, one hellbent on proving that the Man of Steel is an outdated, useless relic. While Supergirl never captured the full impact of the critically adored Action Comics #775 (which inspired the episode “Whatever Happened to Truth, Justice and the American Way?”), transforming Manchester into a Martian Manhunter villain generally worked well. The worst that can be said is that Manchester sort of dropped out of the running very abruptly in “O Brother, Where Art Thou?”.But Season 4 saved its biggest guns for last. The series finally paid off on Season 3’s cliffhanger, introducing Kara’s twisted doppelgänger Red Daughter and revealing she, Agent Liberty and Eve Teschmacher (Andrea Brooks) to be pawns of none other than Lex Luthor (Jon Cryer). After alluding to Superman’s greatest nemesis for years, the series not only brought Lex into the fold but molded him into the first truly great, season-ending villain the series has had. Cryer’s casting turned a lot of heads initially , but it didn’t take him long to make this iconic character his own and establish himself as the most forceful presence in the show’s ensemble cast.Before getting into how the finale tied all of this together, I do want to mention the actual heroes of the series a bit. Melissa Benoist continues to be a crucial part of the series. Her warmth and inherent likability make her an ideal Supergirl, even as this season also allowed her to flex some darker muscles as Red Daughter. Lena (Katie McGrath) also fared well throughout the season, especially as her brother’s surprise return made her life a living nightmare.And as sad as it was to see Jeremy Jordan’s Winn written out of the picture at the end of Season 3, there’s no doubt that the series is better off for having Brainiac-5 (Jesse Rath) as the DEO’s new resident tech genius. Winn seemingly had nowhere left to go as a character, whereas Brainy brings his own brand of humor and his own foibles to the table. Not to mention his charming romance with another worthy new addition, Nia Nal (Nicole Maines). And beyond her relationship with Brainy, Nia proved to be just the sort of wide-eyed, uplifting character the series needed to balance out its growing sense of darkness.Only Alex (Chyler Leigh) seemed to stumble a bit in Season 4. She had some great moments later on, but the amnesia subplot too often felt like an excuse to drag the character back to square one and prolong her slow journey toward motherhood.All of these many threads paid off in the finale as Lex finally carried out his grand plan and manipulated his way right into the White House. With a secret villain pulling the strings of world governments, exploiting deep-seated fears and racial tensions and using a massive disinformation campaign to gaslight ordinary people, it’s not difficult to see how the series has been drawing from real-world events this year. The show has never been very subtle in that regard, and even less so this season.Not that the lack of allegorical subtlety harms the finale much. Capes and tights stories aren’t good for much if they aren’t about something bigger. If Supergirl struggled in the villain department prior to this season, at least the show has made a regular habit of dipping into the X-Men’s well and preaching tolerance and empathy in the face of a rising tide of fear and hatred. The finale hit home as well as any other episode this season, particularly near the end when it became clear that George Lockwood (Graham Verchere) escaped the cycle of hatred that so utterly consumed his father.It was also fitting that the season-long conflict boiled down not so much in metahuman fisticuffs - and honestly, what little action there was in this episode wasn’t terribly memorable or well-staged - but truth and knowledge. With Supergirl powerless to stop Lex’s rise to power, it fell on Kara Danvers to put pen to paper and expose Luthor for the con artist he is. The idea that one well-sourced article could immediately topple a corrupt government and make the general public come to their senses is… pretty naive in light of current events. But once again, you have to respect the show’s optimism and faith that good always triumphs in the end.What really sealed the deal in this episode, beyond Kara and friends’ hard-won victory, was that final confrontation between Lena and Lex. That was such a great moment between these two estranged siblings. It was disappointing that Lex gleefully killed Red Daughter seemingly without remorse. It would have been nice to see a more human side of the character as he eliminated a woman he essentially raised himself. But we did get that with Lex’s death scene, as he finally, begrudgingly but definitively accepted Lena as someone worthy of being called his sister.Best of all, this scene fueled what is easily the most compelling new plot thread heading into Season 5. Lena finally knows the truth about Kara, and it’s already eating away at her. It was fascinating seeing Lex treat that reveal as one last bit of revenge against his sister before the end. I especially enjoyed that extra layer of irony, with Lex taunting Lena for not seeing the truth right in front of her face, even as he himself has always been too blind to see the obvious truth about Superman and Clark Kent. Lex is going to be difficult to top going forward, but Lena has the potential to outdo even her brother if she makes that final plunge into darkness.With that welcome wrinkle to the status quo, I almost wish this episode didn’t devote so much time to laying seeds for Season 5. That seemed an unnecessary move in light of the Lena/Kara twist. Still, there’s clearly a lot to look forward to come October. J’onn has a new foe who hits very close to home. Leviathan is teased as the next great threat (a twist which must set a new speed record for a comic book storyline being adapted into live-action). And the Monitor (LaMonica Garrett) is busy preparing for the Crisis to come. All the pieces are in place for another terrific season, so long as the series can maintain the momentum it’s built up over the last several months.For more on the current state of Arrowverse, check out our reviews for Arrow's Season 7 finale and The Flash's Season 5 finale , then find out how both shows might be teasing a more interconnected Arrowverse this fall