A pyrrhic victory is one where the winning side loses so much in their effort that it's almost not worth the win. The victors lose a huge number of allies, fail to prevent tragedy, or their victory sets up something much, much worse in the future. Pyrrhic victories are often used to keep things compelling in superhero fiction and to prevent the heroes from having too easy a time of things.
As such, there are several notable pyrrhic victories in superhero TV shows. The heroes manage to save the day or overcome an enemy, but either they or the world suffer a great deal in the process, leaving things on a deeply bittersweet note.
10 Wanda Maximoff Defeating Agatha Harkness Only Sets Up Her Further Downfall (WandaVision)
The stakes of WandaVision only become clear in its final episodes, with dark witch Agatha Harkness attempting to steal Wanda Maximoff's magical powers to bolster her own. This would be bad for the world, but the Marvel Cinematic Universe makes it clear that the alternative isn't much better.
Wanda does manage to defeat Agatha as her family fight off SWORD, but this only leads to greater tragedy down the line. Agatha doesn't manage to become overwhelmingly powerful, but Wanda instead takes the Darkhold from her and flees into seclusion. By the next time she appears in Doctor Strange in the Multiverse of Madness, Wanda has become completely corrupted as a result.
9 The Antimatter Cannon Destroys Most Of The Multiverse (Crisis On Infinite Earths)
The Arrowverse's Crisis on Infinite Earths crossover deals with the Anti-Monitor's threat to the entire Multiverse. He seeks to destroy every positive matter universe in existence. His most useful tool is an enormous antimatter cannon, which can completely eradicate a universe with little effort.
The heroes go to great lengths to destroy this cannon, with an alternate version of Barry Allen sacrificing his life to do so. While they avert complete multiversal destruction, the cannon still destroys most universes in existence before they do. As such, they have only a scant handful of universes to protect for the rest of the story.
8 Soldier Boy Inflicts A Lot Of Damage Before He Goes Down (The Boys)
Soldier Boy spends much of season 3 of The Boys as an uncertain ally of Billy Butcher and Hughie, promising to help them against Homelander if they help him track down and kill his former allies in Payback. By the time of the finale, however, he proves himself to be a major threat, and the protagonists bring him down when he targets Homelander's young son Ryan.
They succeed, but Soldier Boy lives up to his reputation. The fight sees Maeve critically injured and depowered, and Butcher's use of V24 proves devastating to his health. There are also the casualties of Soldier Boy's earlier rampages. They even lose a valuable weapon against Homelander, who is still the overarching threat.
7 The Hand Lose, But The Defenders Lose Plenty As Well (The Defenders)
The Defenders crosses over the protagonists of Marvel's Netflix series as they fight against the Hand. The Netflix series are darker than what's typical for the MCU, and so no one expected a happy, victorious ending. While the Hand are defeated, the Defenders don't come out of the battle unscathed.
Over the course of their battle, the Hand kill Stick and manage to mutilate Misty Knight. Matt Murdock loses Elektra again, and the rest of the team thinks they lose him. Although Matt survives, the world believes him to be dead. He's critically injured and needs a long time to recover afterward.
6 Luther Subduing Viktor Causes The Apocalypse (The Umbrella Academy)
The first season of The Umbrella Academy focuses on the protagonists attempting to resolve their personal issues while several factions work at cross-purposes regarding the coming apocalypse. These two storylines intersect when the protagonists learn that Viktor Hargreeves causes the apocalypse with his immense powers.
When Viktor first unlocks his powers again, nearly killing Allison in the process, Luther tries to subdue him. Although Luther succeeds by squeezing Viktor until he falls unconscious and locking him in a soundproof cell, the victory proves short-lived. It fractures the family further and is Viktor's breaking point for becoming the supervillain the White Violin.
5 S.H.I.E.L.D. Inevitably Falls (Agents Of S.H.I.E.L.D.)
Season 1 of Agents of S.H.I.E.L.D. is an unusual watch because the premise of the show has to radically shift halfway through its first season. Due to the plot twist in Captain America: The Winter Soldier, the characters learn that the organization they work for is infiltrated top-to-bottom by HYDRA, and they're left unsure of who they can trust.
Despite the odds stacked against Coulson's team, they manage to escape the destruction of S.H.I.E.L.D. alive. By the end of the season, they receive personal dispensation from Nick Fury to carry on the organization's work. However, S.H.I.E.L.D. still falls, leaving the world much more vulnerable. The team also loses one of their most valued members as Grant Ward reveals himself as a HYDRA agent.
4 Mallus' Defeat Sets Up A Whole Season's Worth Of Foes (Legends Of Tomorrow)
The ultimate antagonist of season 3 of Legends of Tomorrow is Mallus, a time demon who is managing to wreak havoc on the timeline from within his prison. As such, the Legends gather the totems that can defeat Mallus and confront him within his prison. They take losses from doing so, including major character Rip Hunter, but that's far from the worst fallout.
Breaking into Mallus' prison allows other creatures to escape, falling all over time and wreaking havoc. Much of season 4 of Legends of Tomorrow is spent on the Legends attempting to defeat these creatures, who cause a huge amount of damage with their freedom.
3 Ultron Scours At Least One Universe Of Life (What If...?)
After spending several episodes as a series of unconnected shorts, What If...? brings the plots together when an alternate version of Ultron acquires the Infinity Stones and becomes a multiversal threat. The Watcher has to gather characters from various universes to stand a chance at defeating him, which they do by giving Armin Zola control of his body.
However, the cost of this victory is high. Ultron manages to wipe out nearly all life in at least his home universe, threatens others, and wounds the powerful Watcher. Furthermore, the victory allows Zola and Killmonger to fight over the Infinity Stones, which could prove threatening if either wins and manages to overpower Supreme Strange.
2 He Who Remains' Defeat Creates A Multiversal Threat (Loki)
The latter half of Loki follows Loki and Sylvie as they attempt to evade the TVA and bring down its mysterious leader, He Who Remains. Once they get past Alioth and reach the Citadel at the End of Time, He Who Remains offers them a choice: replace him as the leader of the TVA, or kill him and unleash chaos on the universe.
Despite Loki's best efforts, Sylvie chooses to kill him, achieving a centuries-old goal of hers. However, He Who Remains' words prove true. Killing him allows the Sacred Timeline to branch into a full-blown Multiverse, and allows Kang the Conquerer to seize control of the TVA and threaten all existence.
1 Malcolm Merlyn Manages To Destroy Half Of The Glades (Arrow)
Despite the series' dark tone, Oliver Queen manages to win a number of outright victories in the first season of Arrow. However, the season's villain, Malcolm Merlyn, proves a much more dangerous threat. The protagonists are unable to outright thwart his plans. They seemingly kill him and stop his scheme from succeeding in its entirety, but at a great price.
Merlyn's plan half-succeeds, destroying half of the Glades and causing numerous casualties. The heroes also suffer, with several characters unaccounted for and others arrested or dead, even though a number manage to escape unharmed.