History HeWhoFightsMonsters / LiveActionTV

** ''Series/{{Arrow}}'' gives us [[ComicBook/{{Huntress}} Helena Bertinelli]], who is initially shown as a WoobieDestroyerOfWorlds type because her father killed her fiancee. Naturally, she wants revenge on her father. However, her plot involves [[MoralEventHorizon killing and maiming multiple innocent people.]] [[LikeFatherLikeSon Like Father, Like Daughter]] at its worst.

** ''Series/Batwoman2019''. Kate Kane gives the quote to her evil twin sister Alice (citing Bruce Wayne of Earth-99) after Kate violates the ThouShaltNotKill rule due Alice's manipulations. [[spoiler:Fearing she is indeed becoming too much like Alice, Kate betrays her sister into imprisonment at Arkham rather than follow her down the same dark path.]]

*** The Season 3 episode "[[Recap/BuffyTheVampireSlayerS3E11Gingerbread Gingerbread]]" begins with Buffy's mom finding two young children after what looks like a magical rite. She responds by organizing the other parents in Sunnydale into an organization to go after witches (and Slayers.) The episode ends with them all trying to burn ''their own children'' at the stake.

*** Holtz is so obsessed with obtaining "justice" against Angelus that he followed him into the future, disregarded all the myriad evidence of Angel's reformation, and did all he can to make Angel suffer psychologically. Although, in the end, he seems to make a comeback when he mentions that love has overcome hate. This turns out to be a ruse; he even uses his own death as further fuel to get Connor to take his revenge for him.

* In ''Series/{{Castle|2009}}'', it's revealed that Detective Kate Beckett's mother was murdered as the result of a lengthy chain of events that resulted from a trio of cops who, cynical about the justice system's ability to effectively deal with the mob, eventually went rogue in order to bring them down. In her efforts to expose the people behind her mother's death, it gradually becomes clear that Beckett is beginning to take on several similarities to these cops, including going rogue at times. [[spoiler: It's ultimately subverted; she ends up having an epiphany in which she realises she's in love with Castle and is throwing her life away on revenge and decides to step back and focus on building a life with him rather than spiral into self-destructive obsession.]]
* ''Series/CobraKai'': Johnny sees the results of his dojo at the All Valley Tournament. Miguel, Aisha, and Hawk just wanted to be able to defend themselves against the students bullying them. While Johnny's training helped them achieve those results, it also led to them becoming the similarly ruthless, aggressive brutes that his own gang had once been. And he's like, OhCrap
** Daniel is intensely upset with the restoration of Cobra Kai, only seeing that name associated with the bullies who tormented him. He pulls some business contacts to get the rent raised at the strip mall where Cobra Kai has set up, hoping to drive them out of business with the inflation. He proudly tells this to Amanda, who chastises him over such petty, immature and immoral behavior and not thinking of the people beyond Johnny he was hurting.

** "[[Recap/StarTrekDeepSpaceNineS06E19InThePaleMoonlight In the Pale Moonlight]]" has Sisko resort to several underhand tactics [[spoiler:and eventually condone a murder]] in order to coerce the Romulans to ally with the Federation against the Dominion. The final scene of the episode has Sisko chillingly coming to the realization that he can, in fact, live with what he's done.

* ''Series/VeronicaMars'' implies that Keith and Veronica's career choices are starting to take their toll on the characters' well being and sense of morality.

* ''Series/{{Merlin|2008}}'':

* In the ''Series/StarTrekTheOriginalSeries'' episode "The Savage Curtain", the Excalbians notice that both the "good" team and the "evil" team used the same tactics. Kirk explained it was ''the reason'' that they fought, the Enterprise crew was threatened if the good team didn't fight while the bad team was offered "power" if they won.

** The two-part episode "Homefront/Paradise Lost" features [[spoiler: Admiral Layton, whose concern that the Federation wasn't taking the Dominion seriously enough leads him to fake a Dominion attack, attempt a coup, and order one Starfleet ship to fire on another.]] Luckily, Sisko manages to get in his way.
** "In the Pale Moonlight" has Sisko resort to several underhand tactics [[spoiler:and eventually condone a murder]] in order to coerce the Romulans to ally with the Federation against the Dominion. The final scene of the episode has Sisko chillingly coming to the realization that he can, in fact, live with what he's done.
** "Extreme Measures" has Bashir commit a form of Mind Rape against Section 31 operative Luther Sloan in order to save Odo's life. Sloan himself (and his organization, Section 31) also fall under this trope, doing pretty much whatever they want so long as it's under the pretext of protecting the Federation.

* In ''Series/{{Castle}}'', it's revealed that Detective Kate Beckett's mother was murdered as the result of a lengthy chain of events that resulted from a trio of cops who, cynical about the justice system's ability to effectively deal with the mob, eventually went rogue in order to bring them down. In her efforts to expose the people behind her mother's death, it gradually becomes clear that Beckett is beginning to take on several similarities to these cops, including going rogue at times. [[spoiler: It's ultimately subverted; she ends up having an epiphany in which she realises she's in love with Castle and is throwing her life away on revenge and decides to step back and focus on building a life with him rather than spiral into self-destructive obsession.]]

* Most of the Argent family from ''Series/TeenWolf''. Their role seems to be keeping supernatural creatures in line, but can be just as cruel as the werewolves. Chris Argent is more of a KnightTemplar but has no qualms about threatening sixteen-year-olds. Victoria is fine with torturing ordinary humans that do not even know werewolves exist just to create job vacancies for Hunters. Kate and Gerald were each an outright psychopathic ManipulativeBastard.

-->''Aruto:'' [[spoiler:I am...the Ark...]]

--> Aruto:[[spoiler: I am...the Ark...]]

** Daenerys believes so firmly in SlaveryIsASpecialKindOfEvil that she views any punishment she inflicts on the slave masters as justice.

** ''Series/KamenRiderRevice'' features one of the more explicit examples within the franchise in Junpei Shiranami/Kamen Rider Vail/[[spoiler: Genta Igarashi]]; after the death of his parents caused by a red demon, Junpei, after being saved from death after the incident by [[NebulousEvilOrganisation NOAH]], willingly becomes a the organization's executioner for its failed experiments in order to take revenge against the red demon. However, he eventually becomes so consumed with revenge that he becomes practically indistinguishable from the other demons he hunts down, to the point that one of the terrified civilians he saves from one of his hunts accidently mistakes him for one of those very demons.

* In ''Series/{{Community}}'', this happens to [[SoapboxSadie Britta]], [[BewareTheNiceOnes Shirley]], and [[TheCutie Annie]] when they use [[AmbiguousDisorder Abed's]] BrutalHonesty to take down a number of [[AlphaBitch Alpha Bitches]] who humiliate other women. They end up indiscriminately pointing out the flaws of everyone until it reaches the point [[MetaGuy Abed]] invokes HoistByHisOwnPetard by giving the former {{Alpha Bitch}}es the perfect insults to use on them.

** [[spoiler: Jack Bauer]] takes this trope UpToEleven in the second half of the eighth season when he gets his hands on a murderer. [[spoiler: Jack eventually backs down when he realizes what the consequences (to innocent people) will be if he carries out his revenge, stopping short of falling as far as Tony did]].

* ''Series/{{Oz}}'':

** ''Series/{{Arrow}}'' gives us [[ComicBook/{{Huntress}} Helena Bertinelli]], who is initially shown as a WoobieDestroyerOfWorlds type because her father killed her fiancee. Naturally, she wants revenge on her father. However, her plot involves [[MoralEventHorizon killing and maiming multiple innocent people.]] LikeFatherLikeSon at its worst.

*** Dark Willow started out wanting revenge against Warren for what he did to her girlfriend, Tara, then moved onto his friends because of guilt by association, and soon escalated into CardCarryingVillain territory, until she eventually [[OmnicidalManiac tried to destroy the world]]. Willow was brought back from the abyss by [[ThePowerOfLove Xander]].

*** This literally happened to Forrest.

* In ''Series/{{Castle}}'', it's revealed that Detective Kate Beckett's mother was murdered as the result of a lengthy chain of events that resulted from a trio of cops who, cynical about the justice system's ability to effectively deal with the mob, eventually rogue in order to bring them down. In her efforts to expose the people behind her mother's death, it gradually becomes clear that Beckett is beginning to take on several similarities to these cops, including going rogue at times. [[spoiler: It's ultimately subverted; she ends up having an epiphany in which she realises she's in love with Castle, is throwing her life away on revenge and decides to step back and focus on building a life with him rather than spiral into self-destructive obsession.]]

* ''Series/TheTwilightZone'': In "The Mirror", a rebel overthrows a dictator in a banana republic. However, the dethroned dictator says the rebel will learn the consequences of ruling by force (i.e. killing people to maintain power). The new ruler becomes more and more paranoid, using more and more vicious measures to maintain his rule, proving he indeed became just like the dictator he deposed.

* One of the core themes of the ''Franchise/KamenRider'' franchise is the concept of "does becoming a monster means losing your humanity?" Almost every series has its Kamen Riders' powers come from the same source as the villains in their show [[spoiler: with some even crossing over the line and literally becoming the very MonsterOfTheWeek they've been fighting all along.]]

** Sheridan himself falls victim to this when he suddenly encounters a survivor of the accident that he'd previously believed his wife had died in. In a mad hope that if this man, Morden, is alive, then she might be as well, Sheridan unlawfully locks him up and interrogates at length, dismissing his own crew's objections. Furious by Morden's refusal to cooperate and suspecting him of lying [[spoiler:(he ''is'' lying)]], Sheridan threatens to keep him locked up indefinitely and even ''torture'' him.

** In ''Series/KamenRiderKuuga'', this is [[BigBad N-Daguva-Zeba's]] [[InvokedTrope endgame plan]] for the FinalBattle: if Yusuke ''does'' win their fight, then he'll end up becoming just as bloodthirtsy and violent as he is, and this becoming his successor and going on to bring about the Ultimate Darkness in his place. [[spoiler: However, his plan ends in failure due to him [[EvilCannotComprehendGood being incapable of understanding]] that Yusuke could defeat him without becoming just as bad as him.]]

** In ''Series/KamenRiderGaim'', the world is being infected by plants and monsters from another dimension, Helheim, which [[spoiler:Kaito]] gets to experience first hand early on. After barely stalling the infection for a good chunk of the show's run, [[spoiler:he gives in, consuming a fruit of Helheim Forest and becoming a full-blown Overlord Inves, intent on destroying the world and remaking it into his own image like the previous Overlords that threatened the world.]]
*** [[spoiler:Kouta]] also has to follow in his footsteps - he manages to avoid the slow, painful infection from a wound from Helheim's hostile flora, but the overuse of [[spoiler:[[SuperMode Kiwami]] [[DangerousForbiddenTechnique Arms]] gradually turns him into an Overlord]] as well. Notably, he subverts this trope by keeping morals and herosim, [[spoiler: even after comsuming the Golden Fruit]].
** ''Series/KamenRiderZiO'' is all about preventing this trope from occurring. The story revolves all around Sougo Toiwa, whose dream is to become the greatest king in history. Fast forward to fifty years, he ends up becoming Oma Zi-O an EvilOverlord who proves to be worse than any other villain before him in franchise history, to the point that multip factor go back in time in order to find a way to prevent his rise to power.
** In ''Series/KamenRiderZeroOne'', Aruto Hiden witnesses [[spoiler: the death of Izu at the hands of Horobi]], which sends him into a HeroicBSOD and SanitySlippage so bad that he ends up [[spoiler: becoming Kamen Rider Ark-One, making him become the successor to the BigBad that's been responible for [[MonsterOfTheWeek Monsters of the Week]] that's been plaguing this series, with Aruto going on to ignite a CycleOfRevenge and putting Horobi through what he's been through.]] Notably, this is something ''Aruto himself'' acknowledges after his first transformation.

** In ''KamenRiderZeroOne'', Aruto Hiden witnesses [[spoiler: the death of Izu at the hands of Horobi]], which sends him into a HeroicBSOD and SanitySlippage so bad that he ends up [[spoiler: becoming Kamen Rider Ark-One, making him become the successor to the BigBad that's been responible for [[MonsterOfTheWeek Monsters of the Week]] that's been plaguing this series, with Aruto going on to ignite a CycleOfRevenge and putting Horobi through what he's been through.]] Notably, this is something ''Aruto himself'' acknowledges after his first transformation.