->''"By opening all eight gates, you could attain power beyond even the Hokage. The only drawback is... you die."''
-->-- '''Kakashi''' on the Hidden Lotus technique, ''Manga/{{Naruto}}''

PowerAtAPrice embodied in a single move or technique, a Dangerous Forbidden Technique is an attack that carries a significant risk of harm to it. Maybe it takes a toll on [[CastFromHitPoints the user's body]] or [[WithGreatPowerComesGreatInsanity his mind]]. Maybe it [[SummonBiggerFish summons monsters]] that are hard to control. Maybe it's just [[BadPowersBadPeople immoral]], or it unlocks a SuperpoweredEvilSide. Whatever the reason, it can't be used unless it's absolutely necessary -- usually when the GodzillaThreshold is reached.

A common way to use this trope is for an OldMaster to teach the technique but insist that the hero [[YouAreNotReady isn't ready to use it yet]]. RuleOfDrama indicates that the hero must keep the technique in his back pocket until such time as he has no choice but to use it. It's like a ForbiddenChekhovsGun, except it has a NecessaryDrawback.

Compare DeadlyUpgrade, CastFromHitPoints, CastFromLifespan, CastFromExperiencePoints, SacrificialRevivalSpell, and DeathOrGloryAttack. See also GodzillaThreshold and LethalHarmlessPowers. If a character uses (and survives) the move on a regular basis, it's IThoughtItWasForbidden.

----
!!Examples
[[foldercontrol]]

[[folder:Anime]]
* ''Manga/{{Naruto}}'' has many of these.
** A subset of the Shinobi arts are called the ''Kinjutsu'' -- literally "forbidden techniques". For one reason or another, they cannot be taught or used by the commanding shinobi. Some fatally harm the user, like the Mass Shadow Clone Technique, which launches {{Doppelganger}}s who [[CastFromHitPoints take some of the user's chakra]], which is eventually fatal; a version of this is Naruto's SignatureMove, although Naruto has a superhuman chakra reserve ''and'' a SuperpoweredEvilSide that can handle it. Others are considered unethical, like the Edo Tensei, which [[RiseFromYourGrave resurrects the dead]] at the cost of another HumanSacrifice. Edo Tensei is particularly powerful (effectively giving you a NighInvulnerable army of TheUndead), which increases the temptation to use it, only for the user to find that at its most powerful, [[spoiler:its creations might escape from the user's control]].
** Sasuke's Chidori is only supposed to be used twice. The third time he used it, he would have died if he didn't have a cursed deal which nearly [[GrandTheftMe took him over]]. Since then, he increased his own chakra capacity to the point that he can spam it without any ill effects.
** Kakashi had two forbidden techniques: Raikiri, an enhanced Chidori; and Kamui, which [[OneHitKill sucks anything he looks at into another dimension]]. Both are limited by chakra capacity. He figured out how to increase his chakra capacity (and taught Sasuke how as well).
** Naruto gets his Futon, Rasenshuriken, in the second half of the manga. It's so powerful that it causes widespread cellular damage to the arm he executes it with. The damage is microscopic, so healing jutsus can't repair it, and Naruto's own HealingFactor is so overworked that it [[CastFromLifespan reduces his lifespan]]. Tsunade tells him not to use it again. Then he masters his [[SuperMode Sage Mode]] and perfects it to the point that he can throw it and nullify the risk to himself.
** Naruto's Kyuubi is essentially a SuperPoweredEvilSide; at deeper levels, it also shortens his lifespan. Naruto winds up [[spoiler:befriending the Kyuubi, which allows him access to its full power without having to physically transform.]]
** Tsunade's regeneration jutsu [[CastFromLifespan shortens her lifespan]] as well.
** Lady Chiyo's clan dabbles with using chakra "strings" to control life-size puppets (and in some cases, assist a human by adding their reflexes to the subject's). They began work on a jutsu to truly breathe life into puppets, but stopped when the beta technique had a nasty side-effect of (you guessed it!) killing the user. [[spoiler:Chiyo winds up [[HeroicSacrifice using it]] to save Kazekage Gaara.]]
** Pain has been shown to have [[spoiler:an ''[[WaveMotionGun incredibly]]'' powerful version of his gravity attack that takes off years of his life, but can destroy an entire city in one blast. And he uses it.]] Nagato, on the other hand, is [[spoiler:an Uzumaki, which means he has his clan's longevity]], so he can use it with reduced risk.
** The Dead Demon Sealing Technique summons TheGrimReaper, who takes [[YourSoulIsMine both your soul]] and [[TakingYouWithMe your opponent's]] and forces them to fight forever in its stomach.
** [[spoiler: Izanagi]] allows users to cast genjutsu on ''themselves'' that can briefly override reality. As a tradeoff, [[spoiler: the eyes used to cast the genjutsu will close forever]].
** The Eight Inner Gates (as referenced in the page quote) is a technique that grants exponentially greater strength as each gate is opened, but with increasing strain on the user's body; Rock Lee was almost permanently crippled by using five of them. If all eight are opened, the user becomes physically stronger than any human could be for a few minutes, though the cost of this is [[DeadlyUpgrade dying shortly after]]. When Guy uses all eight gates he becomes more powerful than even [[spoiler:Madara Uchiha, who was hosting the Juubi to boot]], after which his body is so overheated that it starts dissolving into ash while he's still alive. [[spoiler:Naruto stops him from dying, but the character is shown in a wheelchair years later.]]
* The title character from ''Manga/{{Inuyasha}}'' can allow his demonic blood to temporarily dominate him by casting aside his mystical {{BFS}} (or having it stolen); it's a form of SuperpoweredEvilSide. This "demon form" makes him a lot stronger, but his [[DeadlyUpgrade soul decays]] with each use, and he becomes [[UnstoppableRage more bloodthirsty, vicious, and indiscriminate]] the more his demon side takes over. It also becomes easier to activate (but harder to turn off) over time, implying that his demon side will eventually take over completely.
* ''Manga/RurouniKenshin'':
** Kenshin fighting style, Hiten Misturugi Ryuu, has an ultimate technique that involves putting the user in significant danger. If you hesitate for even a moment, you either die or lose your leg. If you don't hesitate, you might still lose your leg. But overall, the style as a whole takes its toll on Kenshin, who [[spoiler:winds up having to retire from swordsmanship for good]]. Shishio used this technique as well, and [[spoiler:as he was in a full-body bandage, he died of heat exhaustion after 15 minutes]].
** Sanosuke's [[MegatonPunch Futae No Kiwami]] becomes one over time due to its overuse. His hand injury was said to be even worse than the damage Kenshin suffered against Shishio. Though his hand never really heals, he finds ways to minimize the damage.
* ''Anime/DragonBallZ'':
** Goku first learned the Kaio-Ken from King Kai, who told him not to use it at more than double capacity. Vegeta proved to be the GodzillaThreshold where Goku used it at triple capacity, which hurt like hell, and then ''quadruple'' during the BeamOWar. After that, Yajirobe made him scream in agony just by patting him on the back. By the time he fought Freeza, he was strong enough that he could use the lower levels without any strain, but Freeza was strong enough that he had to multiply it by ''twenty'' -- the maximum. Not only was it not nearly enough to win, it also left him exhausted and defenseless.
** Tenshinhan's forbidden technique is the Kikoho (Tri-Beam in the dub), which will kill him with overuse or otherwise exhaust him to the point of being unable to fight. [[InformedAttribute Supposedly]].
** The Mafuba (Evil Containment Wave in the dub) is the technique Master Mutaito used to seal King Piccolo. It requires so much energy that it kills the user, as it did to Master Mutaito; when Piccolo comes back, Master Roshi tries it unsuccessfully and dies as well. It turns out [[spoiler:age may have been a factor; Tenshinhan survived trying to use it, although it still left him completely defenseless.]]
** Vegeta has an "Ultimate Final Skill", effectively a SuicideAttack. (Of course, [[SenselessSacrifice it doesn't work on Buu]].) In the games, it's called "Final Explosion" and reduces you to [[HPToOne a single hit point]].
** ''Anime/DragonBallSuper'' gives us Goku's "Super Saiyan God Super Saiyan Kaio-Ken", where he uses Kaio-Ken while in his Super Saiyan God Super Saiyan form. It provides a ''massive'' boost to Goku's power, but has a scant 10% success rate and can potentially kill Goku instantly the other 90% of the time. The technique also leaves Goku weakened, in pain, and unable to effectively use his ki afterwards.
* ''Manga/{{Eyeshield 21}}'':
** The "Devil Bat Ghost" technique causes tremendous strain on the user's knees. Hiruma orders Sena to seal the technique from view; Sena originally thinks it's to stop the competition from seeing it, until he breaks the order and finds out firsthand.
** The "Devil Bat Dive" is a rarely-used two-point conversion technique that requires the runner to leap over both lines, spin, and fall into the end zone, carrying significant risk of injury. Most teams don't bother and just kick the extra point. It's rarely used in [[UsefulNotes/AmericanFootball real life]] for the same reason.
* ''Manga/OnePiece'':
** In general, ''any'' ability gained by Devil Fruit is a dangerous technique. While some have specific drawbacks, they all share one: the user permanently [[SuperDrowningSkills loses the ability to swim.]] Considering that this is an OceanPunk series, that's a potentially lethal side effect. Many pirates are aware of this and use the stuff anyway.
** Trafalgar Law's Devil Fruit, the Op-Op Fruit, allows the user to perform an "Immortality Operation" [[ItOnlyWorksOnce on a single person]]. It grants the target eternal youth, but it costs the user his own life.
** The Alabasta arc introduces Hero Water (or Fatal Elixir), which massively increases all the drinker's physical abilities for five minutes before killing him.
** The Skypeia arc introduces the Impact Dial, which absorbs any force that strikes it and deals it back to the attacker, but also causes a great deal of pain to the wielder's arm. Its cousin, the Reject Dial, multiplies the counter-force by ten. Wiper, a character intent on killing the BigBad of that arc with the Reject Dial, uses it three times and escapes alive despite massive damage.
** Luffy's "Gear" techniques are his SuperMode, and they all qualify.
*** Gear Second allows Luffy to use his legs as a pump to accelerate the blood flow around his body, dramatically increasing his strength and speed. It would kill a normal human, but RubberMan Luffy can handle it, although it does affect his lifespan. Luffy's a {{Determinator}}, though, so that doesn't stop him that often.
*** Gear Third is the next level up; he blows air into his bones, which enlarges his body and makes him that much stronger. However, after only a couple of attacks, the effect would wear out, the air would leave his body, and Luffy would now be Chibi-fied and vulnerable. He learned how to avoid that after the TimeSkip, which introduced...
*** Gear Fourth, where he [[spoiler:inflates his muscles rather than his bones and augments his whole body with Armament Haki.]] This is much stronger than ever Gear Third, and he can even [[spoiler:use it to fly.]] But like Gear Third, it has a time limit, after which Luffy becomes vulnerable [[spoiler:and cannot use Haki for ten minutes.]]
** Chopper's Monster Point form comes from overuse of the Rumble Ball, which allows him to expand his MultiformBalance to seven forms rather than the standard three. The Rumble Ball's effect is already only three minutes, and he can have only one every six hours. If he uses two, he loses control of his transformations. If he uses three, he activates Monster Point, which turns him into an indiscriminate berseker who could {{curb stomp|battle}} either his enemies or his allies. It's also potentially fatal and knocks Chopper out of commission for a while, although he gets a better handle on it post-TimeSkip.
** Rob Lucci's Rokuogan (or Six King Gun) strikes his opponent with a shockwave comparable to that of a Reject Dial, but using it expends a ridiculous amount of energy. Overuse of the technique was enough to give Luffy a narrow window to defeat him.
** The Energy Steroids from the Fishman Island arc give the user extreme power, endurance, and staminy, but at the expense of his lifespan [[WithGreatPowerComesGreatInsanity and possibly his sanity as well.]]
* ''Manga/{{Bleach}}'':
** Ichigo's fight with Byakuya woke up his [[SuperPoweredEvilSide inner Hollow]] enough for it to want to begin taking over his soul. The more he used his power, the stronger the Hollow became. He eventually learned how to master the hollow, which increased his power in battle. However, it could still take over when he was very close to death, resulting in a truly ghastly outcome for everyone involved. [[spoiler: Only when he learned Final Getsuga Tenshou, which was another example of this trope that destroyed his power after use, was his Hollow fully mastered.]]
** In his battle with [[MadScientist Mayuri]], Uryuu activated [[OneWingedAngel Letzt Stil]], considered the last resort of the Quincy. His [[OldMaster grandfather]] had taught him the technique with the stipulation that [[YouAreNotReady he should never use it]] until he found something he was willing to give up his power to protect. Uryuu chose to use the technique prematurely, found out that ItOnlyWorksOnce, and [[BroughtDownToBadass lost all his spiritual powers]]. His father [[ParentExMachina Ryuuken]] turned out to have an even ''more'' forbidden technique that could restore Uryuu's powers, but it was a very brutal process. [[spoiler:In the Thousand Year Blood War, we learn that there is a way to obtain Letzt Stil powers without the one-time-only drawback, but it is forbidden to traditionalists like the Ishidas as unethical.]]
** Certain [[FunctionalMagic Kidou]] are forbidden. Tessai was exiled with Urahara for using a forbidden Kidou that manipulated space-time. Yamamoto used a forbidden sacrificial Kidou, trading his left arm for a massive pillar of fire in [[KillItWithFire an attempt to kill Aizen]]; as an atonement, he never re-grew it.
** Captain Komamura's clan has the Human Transformation Technique, which turns them from anthropomorphic wolves into full humans with a power boost. [[spoiler: It requires literally giving up your human heart, and when the technique runs out, leaves the user as a full non-anthropomorphic wolf]].
* Towards the end of the Chimera Ant arc of ''HunterXHunter'', [[spoiler: Gon forced himself to grow by shortening his lifespan, using all his inborn talent to reach the power that rivals the King of Ants (strongest being as of now), with the possibility of never being able to use nen ever again (and having lifespan shortened)]].
* ''Anime/YuGiOh'':
** Industrial Illusions has the [[IdiotBall decidedly odd practice]] of designing cards "too powerful and dangerous to be used," requiring them to be sealed somewhere or guarded to keep them from falling into the wrong hands. They ''always'' fall into the wrong hands. (It's little wonder why the game is such SeriousBusiness in this series.) Yugi himself seems to be the only one who recognizes the potential danger of these cards; the first thing he says upon winning Osiris from Strings is, "I must be ''very'' careful with this."
** ''Anime/YuGiOhGX'' has the "Cyber Legacy", which Kaiser Ryō inherited. Normally, he and the other duelists in the Cyber-Style dojo (yes, the Legacy is apparently so powerful, you need to train in a dojo to properly duel with it) practice the normal Cyber-Style, but there's another set of cards known as the Cyberdark-Style that's sealed away from even the Legacy's heir due to its immense and dangerous power. [[spoiler:Ryo learns just why it's so dangerous and forbidden [[ThisIsYourBrainOnEvil the hard way]].]]
** In the real game, cards deemed too powerful are forbidden from official tournaments. Unfortunately, they're not always consistent as to what exactly is "too powerful".
* ''Manga/RanmaOneHalf'':
** Ryoga Hibiki's "Shishi Hōkōdan" is a {{Ki Attack|s}} fueled by the user's [[EmotionalPowers depression and melancholy]]. Ryoga tries to increase its power by becoming even ''more'' depressed. Ranma tries this when fighting him but eventually sees the flaw in this strategy -- the winner of the fight will be happy enough to depower it -- and thus creates a much safer (but just as powerful) technique based on boundless confidence.
** Genma developed two such techniques: the [[CombatPragmatist Yamasenken]] and [[StealthRun Umisenken]]. Unusually for this series, they're both lethal and can be used for [[AndShowItToYou ripping out an opponent's heart]], strangling him, or cutting him into itty bitty pieces. Ganma was loath to teach Ranma anything about them, on the ground that they were far too dangerous; he only acquiesced when he learned that Ryu Kumon was using the Yamasenken. Ranma would duel Ryu with the stipulation that if he won, Ryu would seal the techniques forever.
** Parodied with Happosai's "Happo Fire Burst", which was sealed away for being too destructive... when he accidentally [[DirtyOldMan burnt up a recently-stolen brassiere with it]]. He unseals it to punish Soun Tendo and the Saotomes, when it turns out to be nothing more than a fancy name for throwing homemade firecracker bombs around ([[ImprobableWeaponUser which is no less effective]]).
* ''Manga/OutlawStar'''s Caster gun fired spiritual Caster bullets. Each type was represented by a number, although their differences were never fully established. Eventually, Gene realizes that three numbers never come up, so he tracks down the gunsmiths who make these bullets. They each give him one, but they explain that since they draw on the gunner's soul (there being so little mana left in the universe), if he fires all three, he will die. Sure enough, he needs all three, and sure enough, [[spoiler:he dies along with his enemy, but he was in the Galactic Leyline, which noticed that ''everyone'' inside was dead and performed an AutoRevive.]]
* Almost everybody in ''Manga/GetBackers'' has one. Ginji starts going crazy if he is in his Lightning Emperor mode for too long. Ban can only use his Jagan three times a day, once per person per day. Himiko's acceleration perfume strains her body. Juubei's Black Flying Needles are controlled by a large magnet, and the force of the magnetic field wreaks all kinds of havoc on his body and blinds him early on.
* Late in ''Anime/TekkamanBlade'', D-Boy finds that the Tekkaman transformation is slowly destroying his body. Later, he apparently gets better by "evolving" his transformation into the more powerful Blaster mode. Unfortunately, that turns out to be a better example of this, since now he's losing memories whenever he transforms, which for him is even worse.
* ''Manga/MahouSenseiNegima'''s version of BlackMagic seems to act like this. The first time we see it used is when Jack Rakan demonstrates it for Negi and nearly kills himself in the process. Negi then starts undergoing training so that he'll be able to use it safely. We don't see the real direct consequences of Dark Magic, though, until [[spoiler:Negi basically overdoses on magic and is forced to fight his EnemyWithin; even if he wins, he won't exactly be human anymore.]]
* In ''LightNovel/{{Slayers}}'', Lina's Giga Slave is the mother of all [[DangerousForbiddenTechnique Dangerous Forbidden Techniques]]. It consists of [[spoiler:summoning a fragment of the [[{{God}} Lord of Nightmares]] into the physical plane]], so not only will she die if it is miscast, but she'll take the entire universe with her. [[spoiler: Naturally, it's miscast, and only a literal DeusExMachina on the part of the Lord of Nightmares saves the day.]] Ragna Blade also consumes magic quickly enough to put the caster's life in danger if they try to maintain it for too long.
* {{Parodied|Trope}} in ''Manga/TheWorldGodOnlyKnows'': Suffering from DatingSim withdrawal, Keima resorts to "Capturing God Mode" in order to clear his backlog, playing six games at once at blinding speed while still able to react emotionally to each one. He claims that an hour will cause the use to lose three years of his life (or at least be tired enough to feel that way). He eventually passes out under the strain. That doesn't stop him from hitting ''24'' games at once later in the series.
* It's revealed in ''Anime/MagicalGirlLyricalNanohaStrikers'' that [[FinishingMove Starlight Breaker]] causes considerable strain on Nanoha's body, and that her constant usage of it, as well as her tendency to use {{Deadly Upgrade}}s, contributed to her being critically injured and hospitalized for nearly a year.
* Jin from ''Anime/SamuraiChamploo'' learns his master's DangerousForbiddenTechnique only by word of mouth, along with (needless) explanation of its danger. During his final episode duel, he has to use it in battle. [[spoiler:He allows himself to be stabbed, and takes advantage of his opponent's position at his side and effective defenselessness (as his sword is stuck in Jin) to strike him down.]]
* ''Anime/ZoidsNewCentury'' has a mecha version: Among the three alternate armours available for the Liger Zero is the [[MechaExpansionPack Panzer armour]], effectively turning the Liger into a walking tank with [[WaveMotionGun huge guns]] and [[MacrossMissileMassacre lots and lots of missiles]]. However, it's so [[DeadlyUpgrade heavy and power-consuming that the Liger can barely move and quickly overheats just from wearing the armour]]. It has to be ejected on the battlefield right after each use to avoid melting the Liger Zero.
* In ''Manga/SoulEater'', using Tsubaki's [[spoiler:Uncanny Sword mode]] takes a toll on Black☆Star's health. Early on, he can only maintain it for a short duration before passing out. At one point, the normally submissive Tsubaki refuses to use it out of fear for her partner's well-being. [[spoiler: Eventually, he finds a way around this, at which point the mode apparently stops having a dangerous effect. Really, all it needed was for Black Star to ''listen'' to others (namely Tsubaki) in order to have a chance of working out the technique, rather than assuming it took only physical strength. Being [[JerkWithAHeartOfGold a decent guy really]], he manages it.]]
* ''Franchise/SailorMoon'':
** Sailor Pluto will die if she uses her power to stop time, and Sailor Saturn, who will die if she uses her power of destruction. They [[spoiler:both break the taboo in the [[Manga/SailorMoon manga]] anyway and actually do die -- in Pluto's case for a whole arc -- before coming back fairly nonchalant and well-adjusted about the whole thing.]]
** [[Anime/SailorMoon The anime]] gives us the Silver Crystal, which at full power equates to a KamehameHadoken and kills the user nine times out of ten. But they get one lash wish, which is usually enough to reverse it; Moon got her normal life back and it was enough for her, Mamoru and the Senshi to be revived, even if with TraumaInducedAmnesia until some time later.
* In ''Manga/YuYuHakusho'', Hiei's Dragon of the Darkness Flame is an absurdly powerful technique that summons a dragon made of insanely hot hellfire that incinerates pretty much any enemy that comes into direct contact with it, even fire-resistant demons. The catch? If the user isn't sufficiently powerful, the dragon can turn on the caster and devour him. And the first time Hiei used it, he had to offer his right arm as a sacrifice. [[spoiler: Also subverted, as the one moment the attack ''is'' turned on Hiei, he's become powerful enough to control it, not only surviving, but also temporarily absorbing it into his body, becoming much, much more powerful.]]
* ''Manga/BlackCat'':
** Train can only use railguns five times per day. In the final battle, he squeezed out a sixth shot, resulting in him unable to perform it anymore. He's not worried, though, since he has already taken care of the BigBad.
** Sven's eye ability makes him very tired after using it, which limits him as well, though his ability isn't near as badass.
* Parodied in ''Manga/NininGaShinobuden'', where the technique that has been "banned ten years ago because it was so dangerous" is [[DuctTapeForEverything duct tape underpants]].
* In ''Manga/CodeBreaker'', Toki Fujiwara's usage of his Gauss Cannon will damage whatever arm that he uses to fire. Ths means he can't fire more than twice overall in a fight.
* Overuse of power in ''Manga/GiantRobo'' can lead to nasty consequences. A mook burns himself to near-ashes with his pyrokinesis trying to keep his buddies warm, Alberto the Shockwave [[spoiler:breaks apart after absorbing the Monster Sphere's energy field]], and several characters' powers run fatal risks.
* In ''Manga/FullmetalAlchemist'', human transmutation is the sole taboo when it comes to performing alchemy, and rightly so. The law of equivalent exchange is strict -- you must sacrifice equal or greater value, and the value of a human life places a horribly high toll on anyone who would dabble in such a practice. While trying to resurrect their mother, Edward lost a leg and Alphonse lost his ''entire body.'' It cost Edward his arm to merely tether Alphonse's soul to a suit of armor in a golem form through a blood seal. And that still wasn't enough for the [[CameBackWrong alchemy to work]].
* ''Manga/SaintSeiya'':
** Dragon Saint Shiryu is warned by his master never to push his fighting technique beyond a certain limit, lest he unleash the "Ultimate Dragon", basically sending himself and his opponent into orbit. Of course, Shiryu ''does'' end up unleashing the "Ultimate Dragon". [[spoiler: But he doesn't die. His opponent Shura has a last-minute change of heart and manages to send him back to Earth with just a very well-timed kick. Seriously.]] That being said, the technique was never used again in the manga. In the [[{{Filler}} next arc]] of the anime, Shiryu attempted it again as a last resort move, but stopped when doing so would destroy a MacGuffin that was needed.
** Athena Exclamation is a technique so devastating, so powerful, it has the power to annihilate the Earth. Therefore, it was declared taboo by Athena's Saints. It consists of three Gold Saints focusing all their [[BattleAura Cosmo]] into a single point, discharging a blast with the same power as the Big Bang itself. Naturally, it was used in the final arc. And once ''that'' taboo [[GodzillaThreshold was broken]], it was used twice more -- by [[OhCrap two opposing trios of Gold Saints]].
* In ''VideoGame/InazumaEleven'', [[spoiler:Teikoku]] has some hissatsu techniques, explicitly called "forbidden techniques", which are extremely powerful but strain the user's body; a single use is enough to cause searing pain, and three uses in a single match is liable to send the user to the hospital with the possibility of permanent injuries.
* Everyone seems to have one in ''Manga/ThePrinceOfTennis'': Tezuka Phantom and Zero Shiki Serve, Ryoma's Cyclone Smash, Atobe's Tannhauser Serve, Sanada's Rai, you name it. The most powerful, though, is "Dash Hadoukyuu", [[TheBigGuy Kawamura's]] most powerful shot [[spoiler: until Final Hadoukyuu]]. The original Hadoukyuu already puts a great deal of strain on the arm, while the Dash Hadoukyuu is restricted to once per match. [[spoiler: Naturally, he breaks this rule against Gin Ishida]].
* The NT-D ("Newtype Destroyer") system in ''Anime/MobileSuitGundamUnicorn''. Built in to the eponymous Gundam, the system activates if it detects a Newtype (or cyber-Newtype) somewhere in the vicinity. It then releases all of the limiters on the Gundam's systems, directly linking all the suit's functions to the pilot's mind. This allows the pilot to gain extreme reflexes, almost mechanical precision, and even [[spoiler:the ability to hijack Psy-Commu weapons, which are generally a Newtype's most dangerous weapons]]. However, this system can override the pilot's own morals with the system's programming to destroy Newtypes, and runs a very real risk of burning out the pilot's mind and causing severe brain damage.
* In ''Anime/MobileSuitGundamAGE'', Kio views the AGE-FX's [[SuperMode FX-Burst Mode]] as one, as he has recently made the switch to [[TechnicalPacifist technical pacifism]], and he [[MutuallyExclusivePowerups can't use]] the [[AttackDrone precision weapons]] necessary to guarantee the safety of enemy pilots while using that mode.
* ''Anime/GundamBuildFightersTry'' has "assimilation", a not-very-well-explained phenomenon where a pilot apparently links his mind to his Gunpla, controlling it like his own body and greatly increasing its performance. Downsides? The pilot incurs actual, ''physical'' injuries when the Gunpla is damaged, and on top of that, using this ability is exhausting in the extreme. There is a real risk of receiving permanent or even life-threatening injuries from this, in a sport that's supposed to be completely harmless (at least, to the people playing it).
* In ''Manga/BambooBlade'' as well as real-life Kendo, the throat strike is treated this way, because of the high risk of seriously injuring your opponent if done incorrectly. In the series, it is used mostly by morally ambiguous or outright villainous characters, although the main protagonist Tamaki will also attempt to use it when sufficiently provoked or against an especially skilled opponent. In real-world Kendo, throat strikes are only permitted to be used only by high-ranking Kendoka.
* In ''Anime/{{Raideen}}'', the titular mecha has the powerful "God Voice" attack, which ends up ruining his vocal cords every time he does it. In the ''VideoGame/SuperRobotWars'' games, Akira will actually end up being unable to speak if you use this too many times before a certain point.
* Few would expect this from an anime about the ''circus,'' but the arc of ''Anime/KaleidoStar'' revolved around one of these. There was a DangerousForbiddenTechnique for trapeze and highwire artists, the [[spoiler: Fantastic Maneuvre]], which was ''so'' dangerous and forbidden, Fool refused to even tell Sora what it was because as soon as she heard about it, she would be so obsessed with it that she'd try it even when she wasn't ready, and die. Attempting this DangerousForbiddenTechnique was what killed [[spoiler: Karlos']] best friend and old partner [[spoiler: Aaron Killian]], becoming [[MyGreatestFailure His Greatest Failure]] and turning him into TheAtoner. [[spoiler: And it drives Aaron's son Yuri to seek revenge against Kalos, taking the Stage away from him because he believes he drove his father to basically kill himself.]] Needless to say, by the end of the first part of the series, [[spoiler: Sora and Layla]] perform it successfully. Doing it even once is enough to [[spoiler: cripple an ''already'' injured Layla for life [[CareerEndingInjury and end her circus career forever]].]]
* {{Parodied}} in ''Manga/DailyLivesOfHighSchoolBoys''' ''High School Boys and the Sure-kill Shot'' skit, when Mitsuo claimed he "sealed" his "reflection shot" because it's too unfair. He's right; the soccer ball reflects because of the piece of plastic he planted on the field. [[ButtMonkey Mitsuo being Mitsuo]], it still got saved by the self-proclaimed NonActionGuy Hidenori.
* Being a {{Deconstruction}} of the FightingSeries PlayedForLaughs, ''Manga/MutekiKanbanMusume'' parodies this trope when Kankuro tries to decide what thing he would imitate to beat Miki.
--> '''Kankuro:''' [[PowerCopying As long as I imagine myself as something before training, Iíll gain both confidence and strength,]] [[VerbalTic nya]]. What should I imagine myself as next, [[VerbalTic nya]]?\\
'''Akihiko:''' Shouldnít you have already decided on that?\\
[''Flashback of Miki being {{Curb Stomp Battle}}d by her mother, a fat restaurant hostess.'']\\
'''Kankuro:''' Thatís impossible, [[VerbalTic nya]].
* In ''Anime/DennouCoil'', there's [[spoiler:Imago, which allows the user of it to effectively become a {{Technopath}} within the augmented reality. However, side effects of using it result in damage to one's body, including [[YourMindMakesItReal heart problems and other nasty effects]].]]
* ''Anime/RebuildOfEvangelion'' brings us [[UnstoppableRage Beast Mode]], which grants the Evangelion a power boost at the cost of potentially contaminating its pilot's mind. It's also shown to be a very PainfulTransformation, for both the Eva and the pilot. Further, even if it is successfully activated, the pilot loses all reason and is only capable of fighting like an enraged animal.
* In ''LightNovel/UnlimitedFafnir'', Yuu is able to obtain tremendous power from an ancient dragon calling itself "Yggdrasil" in order to defeat dragons attacking humanity. Unfortunately it requires his memories in order to summon said powers.
* ''LightNovel/HighSchoolDXD'' gives us Juggernaut Drive, which allows the users of [[EmpathicWeapon Boosted Gear or Divine Dividing]] to completely unseal the Dragon contained within, transforming into a near-unstoppable, monstrous form that goes on a berserker rampage until the user's life is consumed. Both [[TheHero Issei]] and [[TheRival Vali]] have to find a way around this. [[spoiler:Vali has, long before the start of the series -- as a BornWinner, he has a ''stupid'' amount of Devil-power and fuels his JD with that instead of his lifeforce. Issei forgoes the form entirely in favor of creating Cardinal Crimson Promotion, an exhausting but near-equal power boost that relies on his link to Rias, befitting his role as TheChampion.]]
* In both ''Manga/GetterRobo G'' and its {{expy}} ''Anime/{{Gekiganger 3}}'', the Shine Spark and the Gekigan Flare are forbidden, as the three pilots have to hit a switch ''at the same time'' to activate the attack or risk destroying the robot.
[[/folder]]

[[folder: Comic Books ]]
* In the Marvel universe, there exists a weapon called the Ultimate Nullifier which can RetGone anyone or anything the user chooses. But if the user doesn't visualize the target properly, then ''the user'' is erased. This is possibly the only weapon that can truly defeat ComicBook/{{Galactus}}. (Possibly. He is known to be afraid of it, at least. Whether any mortal would actually be capable of perfectly visualizing Galactus is dubious.)
* The "Demon Ball" technique in ''BowlingKing''. Its creator injured himself badly attempting to perfect it and was forced to retire from professional bowling.
* In the ''ComicBook/BuffyTheVampireSlayer'' prequel comics, there are dark magicks that the Watchers are forbidden to use. Someone does it anyway, and gets revealed by Giles. But Giles had also used a forbidden technique to reveal the guy, which is why he gets put through a torturous test that either drove everyone else who took it insane or killed them outright.
* ''ComicBook/TheMightyThor'' supporting character character Beta Ray Bill is a cyborg whose body was built with [[PowerLimiter safeguards to prevent his internal reactor from overloading]]. By releasing these safeguards, he can multiply his power by many times. The drawback is that after a few minutes of this, his reactor will reach critical mass, with [[PowerIncontinence explosive consequences]].
* The Human Torch of the ''ComicBook/FantasticFour'' can release a blast of nova-intensity heat, which was very dangerous to do in his earlier days (one issue even stated that releasing it at maximum power would instantaneously kill every living thing in the same hemisphere of Earth as him). Later subverted as he learned to control it better, making collateral damage no longer a serious problem.
* Borderline example with Nightcrawler of the ComicBook/XMen; he can carry someone else with him while using his mutant ability to teleport, but the strain is, in his words, "murderous", both to him and the passenger. Doing it more than once would likely kill them both.

[[/folder]]

[[folder: FanWorks ]]
* FanFic/AGrowingAffection has a few:
** Naruto's original technique, the Blood Clone Jutsu uses blood to form clones almost as tough as the creator, that return any leftover chakra to the original when the technique ends. But the amount of blood required means that anyone without a healing factor would pass out creating more than one Blood Clone. [[spoiler: Naruto creates a stronger version that has Sakura and Ino heal him and give him plasma pills so he can make a small army of blood clones.]]
** Breaking the Souhi is not unlike the retributive strike below, it (according to lore anyway) instantly reduces the temperature of everything in a five kilometer radius to -100 degrees (Fahrenheit or Centigrade not specified), including whoever breaks it.
* Twilight mentions in ''Fanfic/GettingBackOnYourHooves'' mentions unicorns have more potential magical power than they can safely use, which operates on the same principle as muscles being capable of far more than they can safely use. Using their maximum power would drastically increase what they can do, but at the risk of damaging or breaking their horn. [[spoiler:At the finale, [[BigBad Checker Monarch]] does this after her EngineeredPublicConfession in an attempted TakingYouWithMe on Trixie and the mane cast. It not only fails, but her horn is badly damaged as a result.]]
* In ''Fanfic/{{Pokeumans}}'':
** [[SpiritAdvisor Spiritus]] reveals to Brandon that as an Energy Channeller he may be able to perform Total Absorption - which would consume the enemy's aura (and by default, [[ThouShaltNotKill is totally fatal]]) and [[WithGreatPowerComesGreatInsanity may even take a hit on his sanity]] to the point of unleashing a SuperpoweredEvilSide.
** Rikuto of the Long Island Elite Four apparently knows many of these, but must restrain himself from using because, well, he can't kill all of the base's most promising battlers whenever they fight him.
* Parodied in a ''Fanfic/JusticeSocietyOfJapan'' omake, where [[DragonBallZ Mr. Satan]] and [[StreetFighter Dan Hibiki]] both claim to know one of these, but are both too scared to actually perform it.
* ''FanFic/TheLegendOfCynderSeries'': Myst's fury, after she takes a potion to help cure her blindness. The potion has a side effect of drastically increasing a dragon's powers the more they drink; Myst needed to drink a whole bucket's worth to purge The General's poison that was blinding her out of her body. It's heavily implied that Myst's fury would be one of the single most powerful attacks in the entire fic series. However, it would have the unfortunate side effect of killing her if she were to release that much power at once. As such, she has never once used it so far.
* In ''[[FanFic/SovereignGFCOrigins Origins]]'', a ''MassEffect''[=/=]''StarWars''[[spoiler:[=/=]''[=Borderlands=]''[=/=]''[=Halo=]'']] MassiveMultiplayerCrossover, Dr. Kevin Filner comes up with one. In order to fight [[spoiler:the Flood]] the heroes need ships that don't have crews. Unfortunately, all the power sources that have been used for various warships so far are either inadequate or run on some form of {{Unobtainium}} like hypermatter. Consequently, he suggests using biotic batteries, like a certain [[HeelFaceTurn villain-turned-at-least-nonthreatening]] -- Sarah. He repeatedly lampshades how much trouble he will be in for suggesting such a thing, and considering these are [[MamaBear Jack's]] students we're talking about, he's probably right.
* Subverted in the ''{{Manga/Naruto}}'' story ''{{FanFic/Vapors}}'', where the Hiraishin should be this given the numerous ways to TeleFrag yourself or worse. In fact, it has several safeguards built in to avert this, although using it [[spoiler: with cranial hemorrhaging]] is still a very bad idea.
* ''[[https://www.fanfiction.net/s/10092339/1/Ranma-Saotome-Chi-Master Ranma Saotome, Chi Master]]'' has the Black Dragon Breath Technique, which greatly increases the amount of chi the user has at his or her disposal, and automatically channels it into a dragon-shaped battle aura around the user. The drawback is that it puts a ''lot'' of stress on the user's body. Since the battle aura is so compact, it eventually causes the user's muscles to tear themselves apart. Even worse, the breathing exercises required to maintain the aura starts rupturing the blood vessels in the lungs after a while, eventually causing the user to drown in his or her own blood.
[[/folder]]

[[folder:Film]]
* The entire point of TheDarkSide in ''Franchise/StarWars''. [[AllThereInTheManual The Expanded Universe]] defines the most powerful lightsaber form as [[AxCrazy Juyo/Vaapad]], a Sith technique which [[PowerAtAPrice relies on the heavy use of aggression]]. For that reason, it's forbidden to most Jedi except those who demonstrate they're capable of handling it safely -- ''i.e.'', without slipping to the Dark Side.
* In ''Film/KissOfTheDragon'', JetLi describes the titular technique as "very secret, very forbidden". The technique actually poses no danger to the user; it is forbidden because of its effect on the target.
* In ''Film/BladesOfGlory'', the Iron Lotus is a technique developed by the coach in his "wild youth", but only one country was crazy enough to try it -- North Korea. The only attempt resulted in the woman's head cut off by the man's ice skate (as impossible as this sounds). According to the coach, the only way for the technique to be performed successfully is by a pair of two men.
* In ''Film/ManOfTaiChi'', Tiger's master's ultimate move qualifies due to its obscene killing power. When his master ''pulled'' the attack and didn't even make physical contact with Tiger, it still left severe bruising and caused BloodFromTheMouth.
* Shows up early in the first ''Film/TheFastAndTheFurious'': Brian, in his first drag race, uses his nitrous too early and is in danger of losing the race. In desperation, he uses a second nitrous burst, still loses, and severely damages his engine as a result. No one in the entire series of movies ever uses nitrous twice, except for this one instance.
* ''Film/{{Ghostbusters 1984}}'': The Proton Packs fire a stream which can snag a ghost like a lasso. But the device is very unstable, and if the proton streams met, it would cause a "total protonic reversal", leading to all life coming to an end simultaneously and every molecule in the user's body to explode at the speed of light. [[spoiler:They're forced to use it to end Gozer's threat at the end of the first movie. Thankfully, all it does is cause a big boom and cover New York in marshmallow.]]
* In ''Film/AntMan'', going beyond subatomic size can only be accomplished by disabling the suit's regulator, which means you aren't coming back once you do. [[spoiler:Scott finds a way to do it, though, albeit requiring a specific setup]].
* ''Film/CaptainAmericaCivilWar'': [[spoiler:Scott turning to giant size]].
-->'''Ant-Man:''' I've got something that will work! Assuming it doesn't tear me in half.\\
'''Captain America:''' ...you've done this before?\\
'''Ant-Man:''' Sure, plenty of times! Well, once. In a lab. And, uh, I passed out.

[[/folder]]

[[folder:Literature]]
* Death magic in Creator/LoisMcMasterBujold's ''Literature/TheCurseOfChalion'' causes both the target and the caster to die as their souls are borne off to the Bastard's Hell (when it works at all). Luckily for some so affected, not only is the Bastard's Hell more of AHellOfATime than a FireAndBrimstoneHell, but they don't always stay there, as some of the other gods may take them up. This also means while unsuccessful attempts or research are regarded as attempted murder (at least) and dealt with by temporal authorities as such, ''successful'' attempts are not prosecutable -- not only because there's nobody left to prosecute, but also because if it works, it's considered divine intervention.
* Robert Jordan's ''Literature/TheWheelOfTime''
** The use of "balefire" is forbidden by the magic users of the world, and when people use it anyway, they're exceedingly careful with it. Balefire doesn't just obliterate its target, it [[RetGone goes back in time]] to do so, with all the potential paradoxes that implies. Entire cities and their recent histories disappeared from the face of the earth before the mages, good ''and'' evil, decided that maybe gratuitous use of balefire wasn't such a good idea. When Rand begins using it for more than a minute, it is seen as a sign of his rapidly deteriorating mental state impacting his judgement, though he is technically correct that balefire is the only way to ensure enemies such as the Forsaken are not ressurected by the Dark One.
** Picking apart a weave of the One Power rather than leaving it to dissipate is a DangerousForbiddenTechnique among the Aes Sedai, and just a bloody dangerous technique among the Aiel Wise Ones. If executed perfectly, it won't leave a telltale "residue", which normally lets one channeler see exactly what another has done, but failure is extremely easy and can produce a range of consequences, including a lasting "fallout" effect that makes it difficult to cast spells in the entire region for a year or more. [[spoiler:When Elayne tries and fails, it produces a burst of wind. A burst of wind with the force of a small nuclear explosion.]]
* Creator/MercedesLackey's ''Literature/HeraldsOfValdemar'' has the "Final Strike", in which a mage uses up all his energy in an offensive spell, thus killing himself along with whatever is aimed at. It works, too, in the [[DownerEnding tragic]] ending of the ''Last Herald Mage'' trilogy. Elsewhere in ''Valdemar'', [[spoiler: Vanyel's already massive power results in a Final Strike that is so literally earth-shaking that the geography of northern Valdemar is forever altered]], and in the ''Owl Knight'' trilogy [[spoiler: poor old almost-powerless Wizard Justyn must expend his Final Strike to destroy the single bridge that stands between a marauding barbarian tribe and his fleeing village]].
* From the ''Literature/HarryPotter'' series:
** A set of three spells is known as the "Unforgivable Curses"; their use lands an automatic life sentence in Azkaban. This is mostly due to their power; one {{brainwash|ing}}es, one [[ColdBloodedTorture tortures]], and one just [[OneHitKill kills]]. It's impossible to use them without really, truly wanting the consequences, meaning that their use proves the user's malice.
** The use of Horcruxes is so forbidden that it's hard to find any information on how to make one because it involves fracturing the soul, and doing ''that'' involves murdering people.
** The drinking of unicorn's blood grants one life, even when one is all but dead, but at a terrible cost: that one lives a half life, a cursed life, from the moment the blood touches their lips.
* ''Literature/ThePendragonAdventure'': It turns out that [[spoiler: all Travelers can warp reality like [[BigBad Saint Dane]] can, but doing so drains the life force of [[{{Heaven}} Solara]]. Saint Dane avoids these drawbacks by relying on a warped version of Solara based on darkness.]]
* In Anthony Reynolds's ''TabletopGame/{{Warhammer 40000}}'' novel ''[[Literature/WordBearers Dark Apostle]]'', creative thinking is viewed like this by the Mechanicus. Dangerous enough to be sealed away in a separate brain.
* The ''Literature/{{Dragaera}}'' series has "Elder Sorcery", which involves the direct manipulation of raw chaos, and the practice of which is a capital crime by imperial edict. Those who research and practice it do so mainly out of curiosity or the search for knowledge, since elder sorcery has long since been supplanted by the ''much'' safer and easier use "normal" sorcery, where the energy of raw chaos is first filtered through the Imperial Orb before being used. However, there are some circumstances where normal sorcery doesn't work, forcing the characters to resort to elder sorcery.
* In ''Literature/TheMagiciansNephew'', the {{Prequel}} to Literature/TheLionTheWitchAndTheWardrobe, there is a dark spell called the Deplorable Word. When it is spoken, every form of life in the world with the sole exception of the speaker is killed instantly. [[BigBad Jadis]] boasts about the extensive measures she took to learn this and then use it to kill everybody in her homeworld as part of her backstory. [[UsefulNotes/WorldWarII Considering the time Lewis wrote it,]] [[SomeAnvilsNeedToBeDropped it's quite blatant]] [[AtomicHate what it's supposed to symbolize.]]
* ''Literature/TheDresdenFiles'':
** A wizard's death curse. Put simply, the wizard, usually when knowing s/he is about to die, draws up all the power stored in their body and mind and unleashes it in an extremely powerful spell, usually a curse on whoever was killing them. This leaves no energy to keep the brain or heart working, so the wizard dies immediately on casting.
** Hellfire, which is demonic power that enhances spells but only available when your soul is corrupted by a Fallen Angel. Soulfire, Hellfire's divine counterpart, uses the stuff that comprises your ''soul'' as the power source. Use too much Soulfire, and your soul literally evaporates into your spells, killing you (and maybe then some).
* In Creator/GarthNix's ''Literature/OldKingdom'' series, the last of the bells of the necromancer throws everyone that hears it deep into Death, including whoever rings it. There is nevertheless a point in the series where the situation is desperate enough for this to seem like a good idea.
* In ''PerdidoStreetStation'', Isaac relates to Yagharek how a previous administration's Torque experiments were banned once pictures of what that utterly-malignant energy had done to a rival city went public.
* In ''Literature/{{Pact}}'', summoning a demon is actually spectacularly easy -- all you need to do is state their name a certain number of times, and they will come. Of course, there's nothing preventing said demon from immediately inflicting a FateWorseThanDeath upon you if you don't take extensive precautions, and even if ''you'' are protected, a demon is defined by its pure hatred for existence itself, and summoning one will diminish the world as a whole--candles get a little less bright, gasoline lasts a little less long, and people are a little bit worse to one another. [[CrapsackWorld There's no known way of reclaiming what the demons have already taken from the world]]. In some cases, [[RetGone there's no way of knowing what was taken]].
* Creator/JinYong, who writes {{Wuxia}} novels, loves this trope, but none are more (in)famous than the Sunflower Manual/Bixie Swordplay Technique (featured in ''The Smiling, Proud Warrior''), which requires its male adherents to [[spoiler: [[CripplingCastration castrate themselves]]]] and slowly makes the practitioner more and more feminized.
* In the ''Literature/SchooledInMagic'' series, those who perform the necromantic ritual on another person receive vast power which corrupts their mind and destroys their humanity. It is a temptation for many who desire the power, but it is strictly forbidden by all and for all. In this series, fully 2/3rds of the known world is controlled by insane necromancers who the rest of the world is at war with.
* In Creator/PoulAnderson's "The Sensitive Man", the main character's abilities, which lead many to speculate that he's an alien, a mutant, or genetically engineered, prove to be CharlesAtlasSuperpower in the end. He explains how many are found in humans -- mostly psychotics -- and he's learned to draw on them. And since there are good reasons why normal humans can't normally do them, he's about to have a nervous breakdown because of the prolonged usage.
* ''Literature/JourneyToChaos'': Videlct Mens greatly amplifies the might of warriors and mages but overuse of it can kill them or drive them insane. This is why Tiza has to obey a number of rules set by mentor when using it. They boil down to "Don't use it unless you've passed the GodzillaThreshold".
* In ''Literature/FateZero'', Kiritsugu Emiya can use the 'Innate Time Control' magecraft to internally affect time - speed it up for superhuman reaction time in combat, or slow down his bodily functions to avoid a search-and-destroy system. Bad thing, once Kiritsugu stops using it and his body automatically re-synches with the rest of the world, he can suffer ''very'' ugly internal injuries.
* In Creator/LarryCorreia's ''Literature/TheGrimnoirChronicles'', Actives who draw hard enough on their power die. Most who do during the course of the trilogy were already mortally wounded. None of them survive.
[[/folder]]

[[folder: Live Action TV ]]
* ''Series/JukenSentaiGekiranger'' features the Ju-Ju-Zenshin-Hen, which allows the user to take on a super-powerful beast-like form. The bad news: transformation is permanent. The worse news: if your technique isn't perfect, your life's gonna ''suuuuuuck.'' A Wolf Fist user winds up transforming into an out-of-control werewolf periodically, but at least he gets restored into his human form. The Fly Fist user (no, really) isn't so lucky, winding up an anthropomorphic fly who is about the size of a mouse. He ends up getting swallowed by an evil Chameleon Fist user and is resurrected along with her after she dies...
* ''Series/MahouSentaiMagiranger'' also has one. Anyone who uses Chronogel's forbidden time spell will die via getting sucked into a wormhole that appears on their chest while it sucks other things like matter and time into it. This curse was deliberately placed on it - apparently, the use of time magic is so dangerous that ''making sure the universe is screwed if you use it'' is the best way to protect it. Yeeeah.
* Used ''on'' the main character in EliStone. When Eli needs to see the future with more clarity, he asks his acupuncturist Dr. Chen to use a little-known needle combination known as "The Dark Truth." After doing it once, Eli nearly has a heart attack, which makes Chen swear it off. So Eli winds up going to Chen's DistaffCounterpart and rival. He actually has the procedure done at least three times, which is probably why [[spoiler: his aneurysm gets worse by the end of Season 2]].
* L's fiddling with the ''Manga/DeathNote'' rules in the live-action movies could be considered this. There's also the more common in the anime world "technique" of Shinigami intentionally lengthening lives at the cost of their own.
* In ''Series/{{Supernatural}}'', Sam's [[PsychoSerum demon blood]]-drinking to power psychic abilities takes a toll on his sanity and turns him into an out-of-control addict. [[spoiler:It gets worse when it's revealed [[IDidWhatIHadToDo all he did]] was just so he'd be [[UnwittingPawn tricked]] into releasing Lucifer.]] Since then, he went cold turkey (...with some exceptions...). In order to finish the SelfSacrificeScheme to [[spoiler:let Lucifer possess him so he can [[HeroicSacrifice jump]] into Lucifer's [[SealedEvilInACan prison]] and prevent the world from being razed, Castiel says this requires for him to drink A LOT of blood.]] Castiel also hints that [[spoiler:Lucifer's]] current Meat Suit has to drink gallons of demon blood just to keep him in.
* ''Series/KamenRiderDouble'''s Twin Maximum, in which he activates two [[FinishingMove Maximum Drives]] at the same time, temporarily taking his power up to 200%. However, this puts an incredible strain on his body, [[spoiler:as demonstrated when Shotaro impulsively uses it in one battle, which lights him on fire and severely injures him. In the final battle of the series, Double's SuperMode is powerful enough that he can combine the Xtreme and Prism Memories' Maximum Drives without ill effect.]]
* The bonehead maneuver in ''Series/BabylonFive'': Opening a jump gate within an existing jump gate, resulting in a massive explosion of energy that the ship who triggered it is highly unlikely to survive or outrun. The heroes only use it because it was the only way they could think of to shake the Shadow ship trying to kill them. Doubly dangerous, as this destroys the jump gate, leaving the system inaccessible to non-jump drive equipped ships until a (very rare) construction ship drops by to rebuilt the jump gate. On this occasions the planet was already deserted, and the heroes had to additional motive of rendering it inaccessible to grave robbers.
** Sometimes, a deathbed scan is the only way to get critical information. However, telepaths don't like doing them since many describe the experience as having part of them go with the departed. Those that have done four or five are described as being dead inside. Bester has gone on record doing ''eight''.
* Resurrection spells in ''Series/BuffyTheVampireSlayer''. They either turn the dead person into a zombie, or make them come back wrong and all screwed up.
** The heart removal technique for vampires was in the ''Series/{{Angel}}'' half. Most vamps won't go near it because they don't know how long they'll be invincible for, only that it could be minutes, hours or days, and then they die.
** And of course, the [[AllYourPowersCombined enjoining spell]] that the Scoobies use to defeat Adam. Giles' knowledge, Willow's magical strength, and Xander's [[TheHeart heart]], all combined with Buffy's super strength and resilience into one nigh-invincible Slayer, complete with {{Voice Of The Legion}} and [[GlowingEyesOfDoom Golden Eyes Of Doom]]? Cool. Being stalked and almost killed by the First Slayer [[YourMindMakesItReal in your dreams]] afterwards because the spell disturbed her spirit? Less cool.
* In ''Series/GameOfThrones'':
** In a rather borderline case, Stannis uses this via Melisandre's [[spoiler: [[LivingShadow shadow assassin]]]] which [[CastFromHitPoints consumes his own energy]]. After using it, Stannis is [[RapidAging noticeably aged]] and Melisandre refuses to do it again because it could kill him.
** Daenerys, lets Mirri Maz Duur [[spoiler: cast a dangerous spell to keep Khal Drogo alive]]. It [[GoneHorriblyRight goes horribly right]].
* In ''{{Series/Merlin}}'', using the Cup of Life to become immortal. The result is that the person who drinks from it becomes the living dead of a sort, not a zombie, but tainted still.
* Subverted in the ''Series/StarTrekTheOriginalSeries'' episode "The Enterprise Incident", where Spock appears to kill Kirk using a powerful Vulcan technique called the "Vulcan Death Grip". In reality, this was part of a plan devised by Kirk, Spock, and Bones to infiltrate the Romulan ship, which involved Spock becoming a FakeDefector; Spock actually only used a more intense version of the more familiar Vulcan Nerve Pinch to render Kirk unconscious and make his vital signs undetectable, claiming he had killed him to win the Commander's respect. There was actually no such thing as a "Vulcan Death Grip". (They were counting on the Commander to not know that, as Kirk later told Nurse Chapel.)
* The ''Series/StarTrekTheNextGeneration'' episode "The First Duty" involves a maneuver called the Kolvoord Starburst, which is forbidden because the last time it was attempted a century earlier, all five cadets were killed. [[spoiler: Turns out it was attempted again, and another cadet paid the price.]] What made the Kolvoord Starburst so dangerous was that not only did it require ''very precise piloting'' so that you don't crash, you also have to open up the plasma vents of your shuttlecraft and ignite it. Thus, you either can wreck or get roasted alive. [[spoiler:The poor cadet panicked and ended up crashing, taking out the other shuttles. The other four got out with their lives, he didn't.]]
** There's also warp speed saucer separation. This is because the moment the saucer leaves the stardrive it immediately starts losing speed. If they don't pull the stardrive away in time, they would crash.
* ''Series/OnceUponATime'' has a couple:
** The Dark Curse (the spell which kicks off the events of the series) is one of only a few reliable ways of traveling between worlds. However, even most of the villains in the Enchanted Forest are too afraid to use it, since activating it requires killing the person you love the most. Regina's desire for revenge on Snow White pushes her to the point of using the spell in the flashbacks of the first couple episodes. This is something of a variant because, rather than being dangerous for the user, it's dangerous for those around them; however, it may still count as Maleficent implies that the actions necessarily will result in permanent psychological damage.
** There's also [[spoiler:the time spell Zelina creates in the Season 3 finale. Magic users in Oz discovered the secret to traveling through time, but repressed the knowledge because of how dangerous it was (when Emma and Hook inadvertently use it, they nearly pull a [[Film/BackToTheFuture Marty McFly]] and prevent Snow and Charming from meeting; this could have caused Emma, and quite possibly all of Storybrooke, to cease to exist had they not rectified the situation). Like her sister, Zelina's desire for revenge pushed her to take such action.]]
[[/folder]]

[[folder:Multiple Media]]
* Nova blasts from ''Toys/{{Bionicle}}'', during which the Toa unleash all of their ElementalPowers in a [[FantasticNuke massive explosion]]. Not only does it leave the Toa with no power left, depending on the type of element it can also easily kill anyone in a close (or even not-so-close) vicinity.
* In the ''Franchise/MonsterHigh'' franchise, Frankie weaponizing her body's electricity by swapping the bolts on her neck is shown to be this, as when she does it on her grandfather's rampaging robot she consequently suffers a HeroicRROD She gets better through ThePowerOfLove.
[[/folder]]

[[folder: Professional Wrestling]]
* Some moves can cause lasting damage to the performer's body. The two most glaring examples are the moonsault and the tombstone piledriver, both of which involve landing full force on the knees. The repeated stress of the latter move is why Wrestling/{{Kane}} switched finishers to the chokeslam and why Wrestling/TheUndertaker developed the Last Ride.
** Speaking of the piledriver, an actual piledriver (not the tombstone version that the Brothers of Destruction use) is something that WWE superstars haven't been allowed to use for over a decade due to Wrestling/OwenHart using the move on Steve Austin, giving him the neck injury that would eventually end his career (no offense to Owen). Come 2013, the fact that Wrestling/CMPunk used it at all, let alone on Wrestling/JohnCena (who's had a history of neck problems), upped the HolyShitQuotient of the match they were in. Said match is now considered one of the best TV matches in RAW history.
** Wrestling/HulkHogan with the Legdrop and Wrestling/StoneColdSteveAustin with the Stone Cold Stunner. Landing directly on your ass hundreds of times a year must be great for the spine and neck (yup, they're connected.) But perhaps we should just cut this off right here and now and say that wrestling in general will pretty much fuck you up over time.
* Most aerial techniques, but the 450 Splash and the Shooting Star Press are really bad; not only do they wear your body down over time, but messing up could seriously hurt you on the spot. Just ask Wrestling/BrockLesnar.
** Wrestling/BookerT's Harlem Hangover (a top-rope flipping Guillotine Legdrop) combined the wear and tear of aerial moves and legdrops. Back problems caused him to abandon the move after only a few years of use.
* The diving headbutt, and German Suplex (which puts a lot of pressure on the spine), especially nasty since they were both moves that Wrestling/ChrisBenoit used...a lot.
* Technical wrestlers generally avoid this as most submissions don't actually put that much pressure on the body. That said, WWE has discouraged many holds which involve the user bridging on their neck, often making mat segments less impressive than those of the other majors.
* Certain moves can get banned as part of a wrestling angle, usually by a heel authority figure.
** At the 2007 Survior Series, Wrestling/ShawnMichaels and Wrestling/RandyOrton faced each other in a title match where Michaels would get disqualified if he used his finisher, the Sweet Chin Music. To even up the odds, however, Orton's championship would go to Michaels if he got himself intentionally disqualified or counted out. [[spoiler: Orton won the match due to Michaels getting distracted trying to use the move but stopping himself, but then used it on him after the match was over.]]
** In 2008, Wrestling/VickieGuerrero banned The Undertaker's then-recently-added submission move Hell's Gate. Her reasoning was due to it causing superstars to get injured and cough up blood. She would strip Undertaker of his World Heavyweight Championship for creating it in the first place, and the ban wouldn't get lifted until over a year later by Teddy Long.
** In 2011, Vickie would strike once again, this time banning Wrestling/{{Edge}}'s spear briefly, and firing him for using it. One week later, Teddy Long once again lifted the ban and reinstated Edge.
** In 2012, after Sheamus accidentally hit Ricardo Rodriguez with a brogue kick instead of intended target Wrestling/AlbertoDelRio, Del Rio and David Otunga tried to push general manager Booker T to ban the move. Booker briefly banned it while investigating whether or not to ban it permanently, but shortly after pointed out that they should understand the risks involved in pro wrestling, and lifted the ban on the move.
[[/folder]]

[[folder:Sports]]
* The ''barra vasca'' style of javelin throwing. Originally stemming from a Basque martial art, it is basically throwing the javelin as if it was a discus. The ''barra vasca'' is an immensely effective style, and a new world record was immediately made. The Finnish javelineers got enthused about this style, and pushed it UpToEleven by soaking their throwing hands in soapy water, inventing the "soap style" with which the javelin flew well over 95 m. Needless to say, the accuracy of ''barra vasca'' style is appalling, and only some 10% of the throws ever got in the sector -- some throws even landing in the grandstand, endangering the spectators. The style was explicitly prohibited beginning with the Melbourne Olympics in 1956.
* Amusingly, many then standard pro wrestling moves such as any an all elbow strikes, headbutts and [[KickThemWhileTheyAreDown kneeing the heads of downed opponents]] were quickly outlawed in Shooto's formative years. There was an on going debate regarding punching the back of the head for fourteen years before it was officially banned too. In the wider mixed martial arts community branching out from Shooto, the debate is over whether to ban ankle locks or not.
[[/folder]]

[[folder: Tabletop Games]]
* ''TabletopGame/DungeonsAndDragons'':
** There exist two magic staffs in the game, the ''staff of power'' and the artifact ''staff of the magi'' which, while very powerful items in themselves, can be broken for a "retributive strike" which releases every spell inside the staff at once, centred on the caster. Given that the SquishyWizard is the norm in D, anyone attempting this strategy had better hope that the 50% chance of getting sent to another dimension comes up.
** There also exists an incredibly powerful dispel spell called ''Mordenkainen's Disjunction'', which can destroy just about any magic effect, even those created by gods. If it is used for this purpose, however, the caster may permanently lose all his magic abilities and/or anger the effect's creator. And he is no slouch, believe us.
** This is the point of the corrupt spells in the ''Book of Vile Darkness'' (and their ''Exalted Deeds'' counterparts, sacrifice spells). They are notably more powerful than other spells of their level--for instance, run-of-the-mill Blindness is a second-level spell, while Seething Eyebane, a corrupt first-level spell, causes the target's eyes to spew acid and explode--but there is always a tax, sometimes permanent, on one or more ability scores. The most powerful of these spells is harmful even to prepare and has a very good chance of rendering the caster dead and/or permanently insane [[OmnicidalManiac (if he wasn't already)]].
** Something else mentioned in the ''Book of Vile Darkness'' is the ArtifactOfDoom called the [[NamesToRunAwayFromReallyFast Death Rock]]. Artifacts are always dangerous, but this one is worse than most; it's history does say that its owners tend to obtain great power and are able to conquer empires, but tend to lose the power at the worst possible time, and are usually overthrown in violent insurrections by their enemies. Here's how the Rock works: It gives the user incredible dark powers of [[{{Necromancer}} necromancy]], giving him the potential to raise vast undead armies. But it has a terrible cost; once a week, it demands the user slay his closest friend or loved one, and claim him or her as a zombie slave. If he is unwilling or unable to do so, the Rock and all powers associated with it vanish. Clearly, all former users never realize that if you are willing to do this, you're going to run out of friends and loved ones ''very'' quickly (a lot of them will likely stop being your friends before you can use them as the required sacrifices) and be unable to make any new ones; on the other hand, you'll probably make hated enemies ''very'' fast...
** Prior to the 2nd Edition, Orcus was murdered by Kiaransalee, the drow goddess of undeath, who usurped his realm in the Abyss. However, in the ''Dead Gods'' module, he CameBackWrong, becoming an undead demon named Tenebrous, possessing a spell called the Last Word that was so lethal, even gods were afraid to use it. This didn't stop Orcus, however. Despite the fact that it was literally consuming him from within, he used it in his camaign to restore himself to life killing several gods using it in order to reclaim [[ArtifactOfDoom his Wand]], and regain his domain in the Abyss. (He succeeding in doing all that, but fortunately, failed in his ultimate goal: becoming a true god.) After gaining back his true form and position, he lost the ability to use it. (The gods have since taken steps to prevent anyone from using it again.)
* In the ''Literature/{{Dragonlance}}'' setting, Wizards of High Sorcery view Primal/Wild Sorcery this way. It was three Sorcerers who, fighting an army of Dragons at the end of the Second Dragon War, caused magical storms that wracked Ansalon. These three Sorcerers ended up becoming the first Wizards after being taught High Sorcery by the gods of magic.
* Several of the noble families from the ''TabletopGame/{{Ravenloft}}'' supplement ''Legacy of the Blood'' possess the knowledge of a DangerousForbiddenTechnique or two, usually in the form of feats that only family members or their elite henchmen can select.
* In the ''TabletopGame/{{Mystara}}'' setting, Glantrians' use of the Radiance is considered this trope even by the Alphatians, who normally consider even the darkest sorts of magic to be permissible. This isn't because it's dangerous to the wielder (which it is), but because [[spoiler: using the power of the Nucleus of the Spheres threatens to drain all magic from the world, bit by bit]].
* In the Sorcerer game from the ''TabletopGame/MageTheAscension'' line, there is one Path that can have this effect: Cursing, which is ExactlyWhatItSaysOnTheTin. Specifically, you can create an absolutely ''vicious'' curse rather than the normal version. The problem is, though, that it renders the caster a vegetable.
* ''TabletopGame/GeniusTheTransgression'' has Deep Inspiration, which lets you draw out Mania directly from the Genius's mind, even if the Genius is "empty". Unfortunately, doing so too often or with too much power runs a very real risk of turning you into an [[InsufferableGenius Unmada,]] and if you keep pushing it even after becoming Unmada...[[TheUnfettered It's a bad idea]].
* ''TabletopGame/ChangelingTheLost'' features Goblin Contracts, magical powers that are cheaper to buy than standard Contracts and have nice effects (open all the locks on a building, see the future, drain an enemy of all their [[{{Mana}} Glamour]]). The catch? Well, they also have side effects that will likely screw you over (respectively, your locks fail the first time someone tries to break in, [[MadOracle you go mad]], you lose all ''your'' Glamour).
** One particular Goblin Contract is "[[TheWildHunt Call the Hunt]]" which has no real catch because it is its own catch; it calls forth a hunting party of [[TheFairFolk True Fae]]. If the changeling who uses it doesn't run away fast enough, he or she will likely be killed or, even worse, dragged back to Arcadia to be tortured once again.
* ''TabletopGame/DemonTheDescent'' features a technique called "Going Loud". In simple terms this transforms your character into their demonic form, sets your magic [[PowerLevel Power Level]] (called Primum) to 10 (out of a maximum of 10) completely refills your Mana (And having maxed Primum means you are able to hold LOTS of Mana) and allows you access to basically ALL of the magic spells in the game. The catch? Well the whole point of this game is that Demons need to impersonate a human in order to avoid the attention of the games BigBad. The human identity they adopt is called their "cover" (in the espionage sense of it being a cover identity). Going Loud irrecoverably destroys that cover, effectively erasing every detail of it from existence, which means that the Big Bad knows ''exactly'' where you are...
* Plenty of Charms in ''TabletopGame/{{Exalted}}'' come with heavy tolls. The more common include pushing up your Limit track, and Abyssals have some that increase resonance or mean that they'll experience CessationOfExistence upon death.
** The Infernal Exalted get a good number of these, mainly because they're learning Charms that make them more like their [[EldritchAbomination Yozi]] patrons. Learn a Charm that gives you increased authority over lesser demons? That means greater demons are allowed to walk all over you. Learn a Charm that perfectly blocks Social attacks? That's because it turns all noise into wretched discord that makes you want to kill. Learn a Charm that allows you to communicate telepathically? Shame you can now only vocalize laughter for the rest of your days.
* The [[WordsCanBreakMyBones Words of Power]] from ''[[TabletopGame/{{GURPS}} GURPS: Thaumatology]]''. Saying one will knock most characters unconscious and the most control you can ever have over a Word is none at all, trying to control it only makes things worse.
* ''TabletopGame/{{Scion}}'' has the Avatars, which allows Gods to channel the power of a Purview at the apex of cosmic power, so much that anyone who fights them has to become one in order to match. However, while the cost to activate it is rather modest game-wise, there are some major prices to be paid: first, you suffer the strongest Fatebinding upon activation, second, if you die, all the Avatars you learned to channel get loose all at once, and third, you activate it in the domain of a Titan, you'll attract every Titan Avatar in it, and chances are, they'll already have their own powers ready as well. Congrats, you now get to fight five or six beings with the same power as you.
* ''TabletopGame/MagicTheGathering'':
** The game has a bunch of cards that are effectively this. You can't miss them, because they all inform you that ''you lose the game'' after a certain amount of time or if a certain condition is met. For example, [[HourOfPower Final Fortune]] allows the user a free turn at a cost and color that doesn't normally get it, but the user loses the game at the end of that turn if they haven't won yet. [[{{Immortality}} Lich and its variants]] protect you from dying through life loss, but kill you under other circumstances, such as an empty graveyard.
** Most Demon Cards and Mechanics play on this in another way; they handicap you in some way or form (such as Echo Costs or requiring you to sacrifice a creature every turn) to maintain their power. The entire concept of Black Suicide builds on this, using cards that have disproportionate amount of power but delayed detrimental effects to win before said detrimental effects does them in. It's referred to as "tearing your arm off and beating your opponent's to death before you bleed out".
** The best definition of this trope is the card Demonic Pact. Each turn, you ''must'' apply one of its effects, but you can't use the same one twice. These effects are draining a sizable chunk of someone's life, making an opponent discard 2 cards, draw 2 cards yourself and ''losing the game''.
* ''TabletopGame/BlueRose'' has Sorcery, generally banned in most kingdoms, to the point that legalizing the ''study'' of sorcery in Aldis has been greatly controversial. While arcana are generally legal in Aldis, sorcery allows an adept to directly harm, control or invade other individuals, mentally or physically, as well as create undead or summon [[OurDemonsAreDifferent darkfiends]], and are considered crimes against all sentient beings. Trying to classify sorcery is tricky, as few arcana are clearly sorcery, and even those that are can be wielded for a period of time without any real damage to the adept if he is sufficiently resilient. Unfortunately, sooner or later, TheCorruption takes hold, and the adept will either fall into the arms of [[DarkIsEvil Shadow]], die a painful death and become transformed into a walking corpse, or try to cleanse himself even as corruption makes it harder. Many people who use sorcery are scrupulous enough to embrace the corruption that comes with it, but the temptation is always there for any arcanist, even those with the best intentions.
* The ''TabletopGame/YuGiOh'' card game has a few perfectly legal cards that could be considered this. One is [[http://yugioh.wikia.com/wiki/Destructive_Draw Destructive Draw]]. It's a Continuous Trap that lets you draw twice during your Draw Phase if you have no cards in your and when you start your turn. ''However'', you take 700 points of damage per turn, and unlike most cards like this, it's possible to lose the duel this way. Also, this card is hard to get rid of; doing so causes the player who uses it 3,000 points of damage.
** At least there are ways to turn that one to your advantage, like Prime Material Dragon. And even worse card is [[http://yugioh.wikia.com/wiki/Lucky_Punch Lucky Punch]]. This is also a Continuous Trap, and it lets you toss three coins once per turn when your opponent attacks. Get three heads, and you get to draw three times. (That's only a 12.5% chance, by the way.) Here's the catch: If you get three tails, the card is destroyed, and if it's destroyed in ANY way, you lose 6,000 Life Points. (Because it isn't considered damage or a Life Point payment, there's really no way to avoid it or convert it to Life Point gain.)
* In ''TabletopGame/{{Ironclaw}}'' [[BlackMagic Unholy magic]] (such as Necromancy, offensive Lutarist spells and a few Druid curses) summons vengeful spirits to do magic for you, there is a chance that these spirits will do other things like animate random corpses, possess people (including the caster), or make scary sounds that freak people out (sometimes to death).
* ''TabletopGame/HcSvntDracones'': Transcendent implants at Cuil 3 or higher generally have a significant chance of causing messy, painful death for their owners, it's guaranteed if someone at Cuil 5 tries to use their implant. Oh, and the Cuil level of an implant temporarily increases each time it's activated in combat.
[[/folder]]

[[folder: Video Games ]]
* In ''Franchise/KingdomHearts'', channeling the darkness is this for most characters. Riku and Terra pay heavy prices for its uncontrolled usage, [[spoiler:getting them both possessed by the BigBad in the first ''Kingdom Hearts'' game and ''Birth By Sleep'', respectively.]] However, in the sequels, [[spoiler:Riku manages to tame the power.]]
** In addition, many of the ''Kingdom Hearts'' villains themselves cannot control the darkness. Maleficent actually appears to Hades and cautions him not to delve too deep at one point in the story. [[spoiler:Ironically, she delves too deep and is slain at the hands of Sora and company (though it should be noted that she had her heart forcibly opened to the darkness by Ansem; she ''is'' GenreSavvy enough to follow her own advice). Hades, while defeated in the Hades Cup, does not die, being a god, and reappears in ''Kingdom Hearts II'' not at all worse for wear.]]
* In the PhantasyStar series, Megid invokes this trope by name. In [[PhantasyStarII PS2]], it's CastFromHitPoints at a painful rate. In [[PhantasyStarIII PS3]] it's only invoked in a cutscene, but when it is, ''it wipes out an entire city in a single casting.'' Note that [=PS3=]'s setting is largely medieval compared to the sci-fi ambience of the rest of the series, so any spell capable of leveling a city is pretty much the equivalent of the Tsar Bomba. In [[PhantasyStarIV PS4]], the negative effects on the player are gone, potentially due to where it comes from and what the stakes are at the time, but it's not easy to access (being guarded by a [[SealedGoodInACan Sealed]] GoodIsNotNice [[SealedGoodInACan In A Can]] guardian who you need to outwit to get it) and the only other user of the spell is the EldritchAbomination that threatens to wipe out the entire star system (and, ostensibly, the universe after that) if you fail in your quest.
* The Chaos Dunk from BarkleyShutUpAndJamGaiden is this for basketball, with the original one wiping out millions of people and getting B-Ball outlawed and [[spoiler:is implied to kill Barkley and Balthios when Barkley uses it to kill Shadow Barkley]]
* ''SonicTheHedgehog'': Similar to his [[SonicX anime counterpart]], Shadow the Hedgehog can gain an extreme power boost whenever he removes the bracelets from his arms. Unlike the SonicX version, however, it doesn't appear to drastically drain his energy. He only used this power once in ''VideoGame/SonicTheHedgehog2006'' to save himself, Rouge and Omega from [[BigBad Mephiles the Dark]], who used two of the Chaos Emeralds to create an army of clones of himself.
** Although not typically portrayed as such, [[GoldenSuperMode Super transformations]] can be this, ESPECIALLY for those who aren't experienced with it. It grants the user invincibility, immeasurable physical and magical enhancement and the power of flight, but it's also tied directly to how many rings the character has on hand. If they burn through their rings, they de-transform and, [[AstralFinale due to the]] [[AmazingTechnicolorBattlefield situations in which]] [[FinalBossNewDimension the form is typically used]], they're pretty much dead. Even when the environment doesn't present an immediate risk, using too much energy at once not only bleeds through the character's stock of rings insanely fast but leaves them on the brink of exhaustion before they even get the chance to de-transform. [[VideoGame/SonicAdventure2 Shadow]] [[VideoGame/SonicUnleashed and Sonic]] have both experienced this and almost died anyway after neutralizing the threat at hand. Furthermore, characters such as [[KidHero Tails]] and [[EvilKnockoff Mecha Sonic]] are so inexperienced with Chaos power that they need not only the Chaos Emeralds, but a secondary source ([[VideoGame/Sonic3AndKnuckles In Tails' case, the Super Emeralds and in Mecha's case, the Master Emerald]]) to even transform in the first place.
* In ''VideoGame/FinalFantasyIV'', the sage Tellah is seeking the ultimate magic spell, Meteo(r), so that he can seek revenge on Golbez (the game's BigBad) for the death of his daughter Anna. Sure enough, Tellah eventually learns the spell from his [[ForgottenSuperweapon repressed memory]], and uses it against Golbez, killing himself in the process. Other, more youthful mages, as well as an eternal precursor, can cast it without side effects. In gameplay terms, this means that he never ends up getting the required amount of MP to cast it.
** In the DS remake, thanks to the NewGamePlus mode the game has, you can easily subvert this: while the items to raise your max MP wouldn't normally be accessible until after his death, they can be carried over from your previous playthrough and indeed, using one on Tellah will allow him to cast Meteor as many times as you want with no ill effects.
* In ''VideoGame/FinalFantasyThe4HeroesOfLight'', the Crystal puts an ominous pause into its usual new-crown recitation by saying "To thee I give this gift of light, upon thy head a crown of... forbidden might" when you get the final one, Dark Fencer. The Desolator spell obtained at the same time is treated in the same way.
* ''SuikodenIV'' offers us the Rune of Punishment, which drains the user's life every time it's used. The rune itself is sentient, and tries to engineer events around it to guarantee it will keep getting used, until eventually its bearer is killed and the rune jumps to a new host, only to begin the cycle anew.
** Interestingly, the Rune of Punishment governs atonement and forgiveness. [[spoiler: if the player is able to forgive the resident backstabbing friend Snowe throughout the course of the game (and he becomes less and less worthy of forgiveness as time goes on, so it's tough) and recruit all 108 Stars of Destiny, Leknaat appears and says that the rune's time of punishment is at an end, and the time for forgiveness has arrived. In addition to unlocking the most powerful rune attack, which greatly damages enemies and greatly heals allies, the improved Rune of Punishment no longer injuries the user for attacks.]] This, of course, implies that everyone that used the rune before was either a) stupid and greedy, or b) unable to understand the proper implications of forgiveness.
** Compare the Soul Eater Rune in the first [[SuikodenI Suikoden]] game, which...[[ExactlyWhatItSaysOnTheTin eats souls]].
* In the ''VideoGame/MegaManBattleNetwork'' games, the Dark Chips are extremely powerful, but that permanently reduce your max HP by 1 with each use. Also, each use drops your KarmaMeter, and enough uses will disable Soul Unisons.
** ''Battle Network 5'' also has Chaos Soul Unisons, which allows you to use a Dark Chip as your charged shot for one round of battle without any of the permanent negative side effects. However, there is a noticeable chance ([[GameBreaker game-breaking glitch]] notwithstanding) that the charged shot will fail and backfire, instead summoning an invincible shadow copy of Mega Man to join the enemies and attempt to beat the crap out of you.
*** Also doubles as DifficultButAwesome, as enough use of Chaos Unison trains the player to be able to use it multiple times in succession without being knocked out of it without PauseScumming, meaning the player can continue charging even if they're being pressed. Shadow Chaos, Knight Chaos, and Magnet Chaos are particularly deadly upon being mastered.
* ''VideoGame/TheWorldEndsWithYou'':
** Joshua uses his [[spoiler:[[BeamSpam Jesus Beam]] attacks to get himself and Neku out of a battle with a Taboo Noise. Though not dangerous in itself, he held back this power until this moment to conceal his identity as the [[{{God}} Composer]], and used this power in the sight of a Reaper, thereby drawing suspicion to himself.]]
** Late in the story, Kitaniji orders all the Reapers to wear special "O-Pins", which Uzuki gleefully describes as granting "unchained power". Kariya points out that there's probably a good reason the chains are normally kept on. [[spoiler:Subverted; as Konishi managed to figure out, Kitaniji ''lied'' about what they do. There's no power boost at all, they're just part of his AssimilationPlot.]]
** [[spoiler:Hanekoma]] later proceeds to [[spoiler:revive Minamimoto as a Taboo Noise]] He reveals this himself to the player in the [[spoiler:[[UnreliableNarrator secret reports]]]].
* Some Techniques and Spells in ''VideoGame/RomancingSaGa'' drain LifeEnergy if one is low leveled in That field of magic or if the weapon uses LifeEnergy for it's techniques.
* ''VideoGame/ValkyrieProfileCovenantOfThePlume'' has a [[PlayerPunch heartbreaking]] example in the Destiny Plume. Left by Lenneth on Wylfred's father's body and corrupted by the goddess Hel, it can make any unit absurdly powerful - ten times as powerful in every single stat. And at the end of the stage, they die. Wyl is forced to use its power on his best friend and would-be {{Lancer}} at the beginning of the game...
** Exactly how forbidden to make it is left up to the player, though, and [[MultipleEndings affects the outcome of the plot.]]
* ''VideoGame/CastlevaniaOrderOfEcclesia'' has the Dominus glyphs; Dominus Anger and Dominus Hatred are direct attack glyphs with each use inflicting shitloads of damage at cost to your HP, while Dominus Agony amps all your stats immensely with gradual HP loss thrown in on top of that. Unless you use a healing item at some point, prolonged uses of these glyphs by themselves will kill you. The Dominus glyph union kills everything in the area--Shanoa included... [[spoiler:...unless you're using it at the end of the final battle, [[HeroicSacrifice when Albus lets his soul be the sacrifice instead]].]]
** Earlier in the series, ''VideoGame/CastlevaniaPortraitOfRuin'' subverts the hell out of this. Pretty much for the entire first half of the game, you get warned about how having Jonathan or any other non-Belmont use the true power of the Vampire Killer will drain their life force and eventually kill them if they overuse it. But when you do actually unlock its power in game, [[DoubleEntendre you can whip it all day long with absolutely no consequences whatsoever.]] Of course, it's possible that [[DoubleSubversion while Jonathan's fine now, he'll suffer its ill effects later down in life]].
* ''VideoGame/BreathOfFireDragonQuarter'' had an extreme version of this. The main character, Ryu, can transform into a ridiculously powerful dragon form at any time which can even floor bosses in a few attacks. However, there's a % counter in the top-right corner of the screen that's slowly ticking towards 100% throughout the game, and using dragon powers make the counter increase much more quickly than it normally does - and if the counter gets to 100%, it's game over. Without dragon powers, the boss fights are quite hard (especially the later ones), so it's down to the player to manage how often they use the dragon powers.
* ''VideoGame/VagrantStory'' has learned techniques that, when used, [[CastFromHitPoints drain a portion of your health]].
* Akuma's (Gouki in the original Japanese) fighting-style from ''StreetFighter'' has the Shun Goku Satsu attack. Until it was mastered by Akuma, it was generally assumed that using it would always be lethal to both. Of course, in-game, it's just a move that does a lot of damage...
* ''VideoGame/TeamFortress2'': There is an unlockable weapon for the Demoman class called The Eyelander, a massive sword which decapitates and heals its user on a killing blow. The downside is that having the sword in your loadout reduces your max HP by 25, because the blade ''feeds on your soul''.
** Averted when, upon killing enough people with the eyelander, the Demoman becomes second in max health only to the Heavy and in speed to the Scout (or a Soldier with the Escape Plan at maximum effect).
** A more appropriate example is the Equalizer. It's possible for a [[JackOfAllStats Soldier]] to [[GlassCannon do huge damage]] when wielding the melee weapon and [[OneHitpointWonder at low health]]. Obviously while powerful, using the weapon this way is very risky, as a casual shot could kill the soldier. Oftentimes cornered soldiers with no rockets use this tactic as a last resort.
** Similarily, the Escape Plan increases the Soldier's speed when wielded as the user's health decreases, allowing the wielder to catch up to a [[FragileSpeedster Scout]] when at less than 20% HP. It also applies a DamageIncreasingDebuff to the user when wielded that persists for a few seconds after being wielded.
** A sillier example is the close combat Ullapool Caber. Is it a [[https://en.wikipedia.org/wiki/Caber_toss giant log]] that takes health of the user when you swing it? No. It's a stick grenade, that you whack people with. It only works once, and you sure as hell are going to feel it if you don't have any bonuses because it explodes in your face. Despite the fact that you are dead if you come across another enemy, it's quite deadly, and can be useful as a last resort or for OHKOs with a critical charge.
** The Boston Basher for the scout is possibly his most powerful DPS weapon, having no damage penalty or crit penalty while being able to inflict bleed damage. However, any attacks that make absolutely no contact will instead hit you, inflicting full damage and bleed on you. On a crit, this can kill the wielder in one hit (although not instantly, but the bleed will do him in if he doesn't find a med kit). If combined with the Crit-a-Cola, this can turn the user into a whirlwind of pain, so long as they never miss.
** The Conniver's Kunai was designed with this in mind; it lowered the user's health so low that a glancing hit from any weapon was strong enough to kill the wielder. This is especially problematic because the class that uses it, the spy, is often in the midst of combat and very likely to get glanced even if the opponent doesn't know he exists. The perk comes that upon a successful backstab, the user gains all the health of the person he just killed. Skilled Kunai users can chainstab through an absurdly large amount of people that they can effectively tank sentries while this happens, which also helps that they also wipe out entire teams with this kind of a maneuver.
* The first four ''[[Franchise/DotHack .hack//]]'' games feature Data Drain, a technique that allows the user to either severely weaken a computer-controlled enemy, or MindRape a human being (most humans hit with a Data Drain end up in comas). The hero, Kite, is the only human with the ability. He uses it to weaken game enemies that have been hacked so as to have infinite HP, thereby making them defeatable, and to gather virus data to hack into protected areas of the game. The catch is that repeated use will corrupt his character data with the virus, causing nasty side effects in battle and, eventually, his character's death.
* Multiple moves in the ''Franchise/{{Pokemon}}'' franchise harm the user (such as [[TakingYouWithMe Explosion]]), but these moves also tend to be very powerful.
** And then there's the move "Struggle," which is a rather weak move that damages the user by 1/4th of it's max HP. Chances are, you're only using it four times before you die. And that's a base case scenario; considering that it's a move that only becomes available when all your other moves are out of PP, odds are it'll do even less than that.
** Focus Punch is extremely powerful, but at two costs. 1. It takes one turn to power up, leaving it open for attack. 2. If your pokemon is hit while powering up it "loses focus" and can't attack.
** And, of course, the classic Hyper Beam and all of its variations. It has 150 base power, but also renders the user immobile on the next turn.
** There's also Curse and Belly Drum, where the user sacrifices half its total HP in order to have the foe lose 1/4 HP every turn or maximize its Attack, respectively. If the user uses the former when they have less than half HP left, they faint; the latter fails when the user is at half HP or less.
** As of Generation V, there's a move called Final Gambit, which causes the user to deal its current HP to the enemy at the cost of fainting. It's also commonly [[SarcasmMode suggested]] as the best move for [[OneHitPointWonder Shedinja]].
** [[OverlyLongGag And then]] there's moves like Overheat and Close Combat, which, while powerful cause Stat drops to the user and leave them vulnerable to opposing attacks.
* In ''VideoGame/NetHack'', one can choose to break a magic wand in half, unleashing all the remaining power at once. Can be dangerous as most wands will simply explode.
* In [[LivePowerfulProBaseball MLB Power Pros]], Alvin has a special pitch, the Mirage Knuckler, but it is extremely dangerous to try to catch it, so much after Alvin and Mark, [[GeniusBruiser the catcher]] train with it for a week, Mark is covered with bruises.
* In ''VideoGame/ValkyriaChronicles'', Valkyrur are already so powerful that not only can they fire huge lasers, NORMAL BULLETS HAVE NO EFFECT ON THEM AND MORTAR ROUNDS CAN ONLY STUN THEM. However, they can sacrifice their life to do things on the scale of annihilating a fort, and the army inside it in a giant blue flame.
* In ''VideoGame/ZettaiHeroProject'' Dangerama's entire skillset is composed of these. As a DeathSeeker, this makes sense.
* BloodMagic is treated as this by most factions in ''Franchise/DragonAge''. It is ''extremely'' powerful and dangerous -- [[BloodyMurder to]] [[MindControl enemies]], [[PoweredByAForsakenChild allies]], [[CastFromHitPoints and the user]] -- and is forbidden virtually everywhere outside Tevinter. While in theory it's no more dangerous than regular magic, the potential for sacrificing or controlling others is considered too dangerous by almost everyone. Even the Tevinter Imperium officially condemns BloodMagic, though in practice all of the Magisters are secretly Blood Mages. The [[WellIntentionedExtremist Grey Wardens]] don't officially forbid it, but many are still leery of it.
* In ''VideoGame/TraumaCenter: Under the Knife'' Derek's senior surgeon forbids him from using the [[BulletTime Healing Touch]] after his first intentional use of it makes him collapse after the operation... with the caveat he's completely aware Derek will merrily ignore this instruction if he thinks the Healing Touch will mean the difference between life and death. This is meant to communicate to the player that they should only use it as a last resort, as doing so will negatively impact their score. [[GuideDangIt Good luck figuring that out without trial and error, though.]] Although the only time that the Healing Touch is actually bad is in ''Under the Knife'', where it slaughters your ranking. Any game from ''Second Opinion'' or later have no penalties to using the Healing Touch.
* ''VideoGame/DungeonCrawl'' has a lot of examples.
** Lugonu's self-banish causes permanent damage to HP and MP.
** As does Borgnjor's Revivification.
** Most necromancy is partially cast from HP.
** High-level summonings can break free and turn hostile at random, and those that can't will instead inflict nasty stuff like sickness and intelligence loss on the caster.
** Downplayed with mid-level summonings, most of which have a chance to be hostile.
* Zed in ''VideoGame/LeagueOfLegends'' is stated to have learned forbidden shadow techniques to defeat his rival Shen, and become a more powerful ninja. It mostly translates to throwing living shadows everywhere.
* An antagonist example: In ''VideoGame/GoldenSun'', shapeshifting into dragons seems to be a DangerousForbiddenTechnique of the Mars Clan of Prox, requiring a great deal of energy and completely wiping out the user's abilities afterward. Saturos even warns Felix in the first game that he and Menardi won't be much help after fighting Isaac & Co. as the Fusion Dragon (which they aren't, though [[DoomedByCanon not for the reasons Saturos had expected]]). [[spoiler: When it's [[BalefulPolymorph forced]] on the antagonists of ''The Lost Age'', they are left without enough power to warm themselves against the freezing cold of the Northern Reaches, and freeze to death. And then the Wise One forces the transformation on ''[[PlayerPunch your parents]]''...]]
* ''VideoGame/TheBindingOfIsaac'' allows players to pick up many upgrades and abilities at random, some of which are very, very powerful. But there are many with heavy, even potentially crippling costs.
** Epicac changes one's tears into a strong explosive attack, at the cost of making them charge slowly and be able to hurt the player. In an added bit of irony, range up effects or upgrades actually make Epicac harder to use, as maxed range makes the projectile detonate far from the player. This means they'd need to hug the opposite wall just to have a hope of hitting a target in the middle of the room.
** The Suicide Bomber vest allows the player to use unlimited explosions, with the downside being they also take the damage. Because, you know, they are detonating bombs strapped to their chest.
** The Devil Rooms usually hold a number of power items, and while they vary from room to room they're relatively consistent. The problem comes from having to sacrifice heart containers to receive them. Not hearts, heart CONTAINERS. The player literally sacrifices their life for power. And that's not counting many of the items they get from the devil rooms have their own disadvantages.
* In each of ''Videogame/EYEDivineCybermancy'''s [[MultipleEndings three main endings]], you are rewarded with a unique and hyper-lethal "Gate" psychic ability. The Hypnotic Gate instantly and permanently paralyzes an enemy, Triangular Gate warps an enemy out of reality, and Substitution [[LifeDrain causes the player to be healed if the enemy takes damage]], and damage the enemy if the player is hurt. All of the abilities are also hyper-lethal for the ''user'', as they have a very high probability to fling the user towards random directions at lethal speeds, [[WithGreatPowerComesGreatInsanity drive them insane]], fry their brains, or cause [[ScarsAreForever permanent trauma]] which hurts stats and persist even after resurrector usage.
* ''VideoGame/{{Ikaruga}}'': "Release the restraint device. Using the released power may result in [[ExplosiveOverclocking destruction of the ship]]".
* In the background lore for ''VideoGame/DiabloIII'', the Wizard character is doing this when he or she expands his/her arsenal to include [[PureEnergy the manipulation of raw mana]] and [[TimeMaster controlling time]], as well as when s/he ignores the normal rules about EquivalentExchange that other casters adhere to in order to prevent magical fallout or corruption. This is why the Wizard is much more destructive than the Sorcer/ess of the past two games.
* The Hell Stringer Technique of the Orphes in ''VideoGame/SuperRobotWarsUX'' is basically a combination attack with the Lyrath that uses the Lepton Vector Engine. Richard uses it to bend the space & time continuum, so he could survive. Richard's body was already screwed up by then and that use pretty much was the final nail.
* ''VideoGame/OdinSphere'' has Oswald's shadow form. In gameplay terms it vastly increases his attack speed and power, at the cost of rapidly eating away as his POW meter (which, if depleted, causes him to become exhausted and unable to move or attack until it refills completely.) In story terms, using it too much will destroy Oswald's soul and turn him into one of the ghostly Revenants haunting Winterhorn Ridge [[spoiler: which eventually does happen in one of the bad ending scenarios, is Oswald is pitted against Onyx.]]
** There's also the Darkova spell, which transforms the user into a massive, powerful cerberus. The former king of Titania used it once to try and fend off enemy forces and went mad with power, ravaging Titania for seven days until he was finally slain by his son. [[spoiler: Ingway finds out how to use it, and it similarly comes back to bite him as soon as he does.]]
* In ''Franchise/TheElderScrolls'' {{Backstory}}, Redguard warriors known as "Sword Singers" could become so skilled with their blades that they were said to be able to [[FantasticNuke split atoms]] using a technique known as the "Pankratosword." It is said that their original homeland of Yokuda was destroyed by this technique, so it became forbidden and was lost to history. (Though the "destruction of the homeland" story is hinted at being an embellishment, and the Redguard people left Yokuda to escape much more traditional violence and oppression.) This being ''The Elder Scrolls'', where lore is often intentionally contradictory, it is left up to the audience to draw their own conclusions.
* A few heroes in ''{{VideoGame/Dota 2}}'' have abilities that are like this. Some examples are Huskar's ''Life Break'', an ability that will deal 35% of an enemy's current HP as damage, but will do the same thing to Huskar himself, and the Techies ''Suicide Squad, Attack!'', which will kill the Techies with a massive explosion, but will also deal massive damage to any enemies in the explosions radius, if not kill them outright.
* In Darkest Dungeon, the Jester class has a move called Heroic End that would be better classified as a harmless forbidden technique. However in the Deepest Dark mod this attack gains incredibly high offensive bonuses against every status effect on the target. The catch is that if there are no status effects on the target it's not much better than a normal attack and using this move at all stuns, debuffs, and marks the user for 3 turns, ensuring anything that survives will focus their attacks on him and kill him before he recovers.
* ''VideoGame/CopyKitty'': The BonusBoss of the game is a techno-magical abomination that wields the ultimate dark magic spell, something called the "Vestige of the Lost". However, even the boss cannot control the full spell, and has to split it into three components which it channels through orbiting altar-like enemies. To defeat the boss, Boki has to [[PowerCopying copy all three component powers]], and then combine them to unleash the spell's full power. [[RealityBreakingParadox The result is not pretty]], though fortunately this all happens in a simulation, so the worst that happens is the sim crashes and Boki gets knocked out.
* The ''Satsui no Hadou'' ("Surge of Murderous Intent") from ''Franchise/StreetFighter''; a dark ki that fighters seeking victory and power can call upon should they be willing to fight without mercy. Gouken hated this aspect of his fighting style and created a fork that does away with it in order to promote humanity and personal growth through martial arts. Despite that, Ryu constantly struggles to avoid succumbing (the endgame being the "what if" character Evil Ryu) and Gouken's brother Akuma has embraced it, despising Gouken for teaching a "softened" art (though he is not entirely in control of it, as Oni demonstrates can happen if he relies on it too much). Techniques that draw upon the ''Satsui no Hadou'' are themselves {{Dangerous Forbidden Technique}}s; being the Metsu Hadoken, Metsu Shoryuken, and Shun Goku Satsu (the last one potentially being lethal to both the victim and user, depending on the contents of the user's soul).
[[/folder]]

[[folder:Visual Novels]]
* In the Fate scenario of ''VisualNovel/FateStayNight'', Saber comes under this limitation because using her Noble Phantasm requires all the mana she's currently holding to activate (and her flawed summoning means Shirou can't provide her with any), and she ends up facing at least three enemies that require -- or at least seem to require -- the use of it to defeat.
** In Heaven's Feel, projection [[spoiler:(more specifically, projection using Archer's arm)]] becomes this for Shirou. While it puts a strain on him in all three paths, this path spesifically gives him a clear limit on usage, and overuse will kill him. [[spoiler:Which it eventually does.]]
** Furthermore, each Servant has a power known as the Broken Phantasm -- willingly breaking their Noble Phantasm. This renders the servant without their proof of heroism (which for many of them is their weapon), but also inflicts massive one-time damage on whoever the Phantasm is shattered on. [[spoiler:Archer, who can create Noble Phantasm duplicates, routinely uses this technique to compensate for the fact that his duplicates are weaker than the real thing.]]
* The protagonist of ''VisualNovel/{{Tsukihime}}'' has the Mystic Eyes of Death Perception, which allow him see the concept of death itself on ''everything'' in the form of lines and points. Observing death, however, will lead to insanity, so he has to use special glasses which block his ability. Every time he takes off these glasses his eyes get stronger, but since humans are not meant to observe the nature of death it puts an increasingly enormous strain on him. In fact, in the [[spoiler:epilogue, which takes place a while after any of the routes, it is revealed in his reunion with his 'sensei' that he is literally on the verge of death, in part due to his ability; it is heavily implied that he actually dies just after they part ways.]]
[[/folder]]

[[folder:Webcomics]]
* ''Webcomic/MSPaintAdventures'' and ''Webcomic/ProblemSleuth'' both feature '''SEPULCHRI-TUUUUUUUUUDE!!'''
** [[ItMakesSenseInContext "No, you fool! Don't you realize if you initiate that attack, it will be the last thing you do??? Fiesta smacks some sense into you."]]
* Webcomic/EightBitTheater":
** '''HADOKEN!!!!''' Although not considered forbidden, Black Mage is only able to cast that spell once a day, and it makes a cute little [[NukeEm nuke-sized]] crater wherever he aims it.
** Spells that drain the net amount of love from the universe with each use and require the sacrifice of orphans to gain in the first place tend to have a bit of a social stigma against them. Black Mage seems to find an excuse to use it nearly every day...but then again, this is Black Mage.
** Also, the Ice-9 spell, which was purely theoretical until Red Mage used it to defeat Kary, the Fiend of Flames. No one had ever cast it up to that point because it would put ''everything in existence'' on ice. Thankfully, RM had a BagOfHolding which contained both Kary and the spell.
* [[Webcomic/LastRes0rt Jigsaw Forte's Zombie Mode]], while not explicitly a DangerousForbiddenTechnique, effectively becomes this when you realize if she uses it ''at all'' while on camera, she's blown her personal {{Masquerade}} (which means if she doesn't die from using it in the first place, ''she will'' when she's done).
** WordOfGod implies that abusing the form does have plenty of consequences, but it depends on how she uses it / how much damage she sustains, not necessarily how often.
* In ''Webcomic/ElGoonishShive'', magic apparently drain users at various rates. Spells too powerful to handle may overtax even well-trained magic users, possibly even [[BroughtDownToNormal removing their magic for months at at a time.]]
* There are several different levels of it in the WhateleyUniverse. Phase has a technique (using his disruption-light level on someone) that runs the risk of corrupting their Body Image Tempalte if they are an Exemplar or Shifter, and turning thme into something grotesque; he avoids it it on moral grounds. Fey has some spells powerful enough that the energy drain will destroy entire ecosystems around her, which is way worse.
* The Forbidden Move in "Webcomic/AxeCop Gets Married": When Axe Cop's opponents at a fighting restaurant in China do a secret move that combines them all into a giant fighter, Axe Cop counters that he knows a move that is ''more'' than secret -- meaning because it's forbidden. The technique has not been explained as forbidden before, but everyone knows about it and panics when he starts to do it, because it will kill everyone in two provinces. The move creates a giant tornado that picks up the adjacent province and smashes your opponent with it. Ultimately {{subverted}}: Axe Cop shows that when done ''correctly'', the move only affects the one opponent, removing everyone and everything else to safety and then putting them back too fast for anyone to notice.
* Jacob from ''Webcomic/DemonFist'' can [[spoiler: teleport]], but doing so damages his body. Using the power to escape with the ''[[CoolShip Hookshot]]'' was what cost him his hand.
* The Shield of Wonders from ''Webcomic/{{Goblins}}'' is an ArtifactOfDoom that casts random magical effects when struck. Simply using the Shield in combat is a Dangerous Forbidden Technique since it's barely less dangerous to the user than it is to his enemies. [[spoiler:Naturally, Complains is forced to use it profusely in a DeathOrGloryAttack, and naturally the shield almost kills him a couple of times and turns him into a half-demon.]]
* In ''Webcomic/{{Heartcore}}'', we have Blast Bomb, Volaster's most powerful spell: upon letting himself be injured to the point where he is bleeding out rapidly, Volaster uses his salamander demon blood to turn himself into a FantasticNuke. In addition to killing himself in the blast, it also damages his Heartcore, which causes his offspring/successor, Carval, to suffer from stunted growth.
[[/folder]]

[[folder:Western Animation]]
* ''WesternAnimation/Ben10UltimateAlien'': Osmosians are aliens that can absorb matter and create something out of that absorbed material (usually armor). They can also absorb energy, but it can turn them AxCrazy. To elaborate, [[spoiler:Kevin absorbed energy from Ben's Ultimatrix to stop Aggregor's plans of bringing forth the]] EndOfTheWorldAsWeKnowIt. [[spoiler:They defeated him alright, but afterwards Kevin went as far as ruthlessly kill whatever comes his way in a rampage out of insanity.]] He was so insane his wrongdoings can be classified as NightmareFuel.
* ''WesternAnimation/AvatarTheLastAirbender'': While it's not really forbidden, lightning redirection (a Firebending technique where you internalize lightning and shoot it in another direction) is extremely dangerous, to the point where even teachers of the move refuse to practice it with their students. First, you have to ''catch'' the lightning, which is just as dangerous as it sounds. While internalized, the lightning must be carefully controlled so it doesn't travel through vital organs. By the end of the series, only three characters know the technique, and only [[MemeticBadass Iroh]] is skilled enough to avoid the dangers consistently.
** [[spoiler: Energybending also carries the danger of mentally and spiritually destroying those who attempt to use it on others if their willpower isn't strong enough. This nearly happened to Aang when he used it on Ozai.]]
** [[spoiler: Bloodbending, supposedly the ultimate technique of waterbending, which involves moving around the blood in a living body and making that body do whatever you want it to do.]] [[spoiler:Like the Osmosian example above, it is shown that it is detrimental to the Waterbender's sanity, making them AxCrazy and power-driven.]]. To elaborate, [[spoiler:Hama was bent on getting revenge after discovering the technique, Katara almost lost herself while trying to avenge her mother, in which she almost lost control while mercilessly bloodbending the Fire Nation's Guards.]]
* Later on in ''WesternAnimation/TheLegendOfKorra'', it's revealed that bloodbending has since been outlawed completely [[spoiler:and for good reason, as even after that its track record didn't get any better: Yakone came out to be an AxCrazy Bloodbender who brought fear to Republic City, and even figured out how to bloodbend without a full moon. Then came his sons, both of whom practiced bloodbending frequently and ended up insatiably power driven later on in their lives, especially Amon]].
* In ''WesternAnimation/HeManAndTheMastersOfTheUniverse2002'' there was the Spell of Separation. Thousands of years before the present day, Hordak used it to divide Eternia into the Light and Dark Hemisphere's, hoping it would transform the Dark half into a realm where he could raise his dark army. But it was more powerful than he had thought, and might have rent the entire planet in two if he hadn't realized it in time and put a stop to it. In the present day, Two-Badd gets ahold of the spell and believes it can be used to separate them back into their original forms of Tuvok and Badka; ignoring He-Man's warnings when he tries to stop them, they gather the three artifacts they need, and the spell is restarted where Hordak left off, forcing He-Man to push himself to his limits and return the three components before it literally destroys Eternia.
* In ''WesternAnimation/{{WITCH}}'', the [[ElementalPowers Guardians]] can choose to transform into living embodiements of their elements, giving them PhysicalGod levels of power- at the risk of losing their personalities and humanity, and being left open to mental domination from outside forces, such as BigBad Nerissa. [[spoiler: Fortunately, the one time they do this, they manage to come back- barely]].
* ''WesternAnimation/ReBoot'': Bob's fusion with Glitch is viewed as doing the unthinkable by Daemon's adviser, and Bob was fully aware that overusing his new Glitch powers would kill him. Bob comes very close to death when Daemon infects and forces him to overuse his powers to create portals. Bob does imply that the fusion would have been much less dangerous had Glitch not been damaged at the time (which is what necessitated the merger in the first place), however.
* ''Franchise/{{Transformers}}'' examples:
** In ''WesternAnimation/TheTransformers'', Elita One turned out to have the power to [[spoiler: [[TimeMaster freeze time]]]], but as Alpha Trion had warned her, using it [[CastFromHitPoints drained]] her LifeEnergy to a near-fatal level.
** Also in ''Franchise/TransformersGeneration1'', Megatron has the ability to draw anti-matter from black holes and pretty much blow up all of his surroundings. It was used about twice in the Marvel comics, where it was explained he didn't often use it because he was liable to kill himself too.
** G1 again, Windcharger can create magnetic fields capable of ripping apart even the strongest of metal structures. It burns him up very rapidly though.
** In ''Anime/TransformersCybertron,'' Vector Prime would [[spoiler: greatly tax himself reversing time by a few minutes, and eventually die by using his time/space powers to get the team through the rift separating Gigantion from the normal universe.]]
* In ''WesternAnimation/JusticeLeague'' [[spoiler:the League had pretty much lost against the Brainiac/Luthor hybrid,]] until ComicBook/TheFlash saves the day by running at extreme speeds (to the point where he was circling the world in mere seconds) [[spoiler:and smacking Brainithor around by repeatedly running into him. Soon enough, he destroys all traces of Brainiac, leaving only a naked Luthor lying on the ground.]] However, in the process he was almost swallowed by the Speed Force from moving so fast, and he says he probably won't be coming back if he ever goes that fast again.
** In another episode, Flash and Luthor [[FreakyFridayFlip get their minds swapped]], and Luthor!Flash is able to run rings around the rest of the League on the Watchtower, in part because he's willing to use superspeed power tricks (such as vibrating objects enough to shatter them) that Flash normally avoids as too dangerous.
* A ''WesternAnimation/BatmanTheAnimatedSeries'' episode has a ninja steal a scroll in Japan that teaches him the secret of a "deadly touch" technique. When Batman faces him off in the end, he tries to avoid being touched by the guy in a specific spot, which (theoretically) would cause instant death. He fails and falls down, seemingly dead. He then gets up and knocks out the bad guy. When asked if the technique was bullshit, he pulls out a [[PocketProtector metal plate]] from under his suit, which has been deformed by a strong force.
* On ''WesternAnimation/RegularShow'', Muscle Man enters a bodybuilding contest, but since he doesn't have time to be fully fit, he concentrates on posing technique. As a last resort, he tries to execute a pose called the Shredder, which if done correctly, will "shred" the competition; but if done incorrectly, it causes the poser to ''explode''. [[spoiler: Muscle Man manages to do it perfectly and wins the competition.]]
[[/folder]]

[[folder: Real Life ]]
* Backfired with the destruction of HMS ''Invincible'' at Jutland. The DangerousForbiddenTechnique in this case was the bypassing of safety protocols designed to prevent flashdown of a detonation in a turret from reaching the magazines, and it was done to increase rate of fire. But ''Invincible'' was pounding the crap out of the German SMS ''Lutzow'', so why not? Why not, indeed. The mist that was hiding her cleared, just long enough for the critically damaged but afloat ''Lutzow''[[note]]At the end of the battle, ''Lutzow'' was too badly damaged to withdraw and was scuttled.[[/note]], along with a second German battlecruiser SMS ''Derfflinger'', to get some solid hits in in the right place, and ''Invincible'' was blown in two. At least one and possibly both of the other British battlecruisers lost that day went up for the same reason. The fact that British ships of UsefulNotes/WorldWarI used a more volatile gunpowder than their German counterparts didn't help, either.
* The [[ExactlyWhatItSaysOnTheTin Mordhau]] ("murder-stroke" or "murder-strike") in [[UsefulNotes/EuropeanSwordsmanship German school of swordsmanship]]. BilingualBonus applies why it is forbidden in friendly combat where the aim is NOT to kill your opponent. True, it may seem odd how, in a fight with big, sharp implements it's [[ImprobableUseOfAWeapon smashing someone with the handle]] that's forbidden, but that thing is heavy, and tends to ignore the fact the victim's wearing metal armor. It has that name for a ''reason''.
* In soccer, the awesome techniques of jumping up in the air and trying to hit a ball next to another player is usually forbidden, because it could hurt the other player if he'd get hit by a flying boot. A little more mild, but still similar is the "scissors" technique of scoring.
* [[NukeEm Nuclear weapons]]. Nukes are capable of great destruction, but actually using one comes at a hefty price. Large nuclear detonations release irradiated material into the surrounding environment that remains dangerous long after the explosion is over. In a more immediate sense, several nations have active nuclear weapons that are kept ready for launch at all times. Since there is currently no viable way to defend against a nuclear weapon after it's been launched, the target has no reason not to fire all its weapons at the aggressor. This is the concept of Mutual Assured Destruction (MAD) and it effectively makes using nukes suicidal. Note that in World War II, this was not an issue; with no other nuclear-capable countries to provide the "Mutual" portion of MAD, the United States was free to attack Japan without fear of a similar retribution.
** Nukes are literally forbidden by international law; even ''threatening'' to use nuclear weapons against another power constitutes a war crime. Though eight nations are declared to have nuclear weapons (and one is suspected) most nuclear powers refuse to consider using nuclear weapons unless someone else does first. Nowadays, the worry is more about the dangers of non-state actors (ie. terrorists) using them instead, which [=MAD=] is essentially powerless against.
** Even nukes aren't necessarily as repellent as biological warfare. At least a nuclear weapon only destroys its targeted area, however horribly; use of biological agents as weapons poses a ''very'' real risk of infecting everyone the contagion touches, be they enemy, ally, innocent bystanders, or one's own side.
* This trope is usually defied in real life, due to [[CombatPragmatist Combat Pragmatism]] being a time-honored military and general combative doctrine. If it's dangerous and highly lethal, using it is the best way to win. If it's forbidden, all the better, because that means the other guy will never see it coming.
* There are international [[UsefulNotes/TheLawsAndCustomsOfWar Laws and Customs of War]], that ban war tactics such as [[ShootTheMedicFirst shooting the medic]] and [[RapePillageAndBurn deliberately harming civilians]]
* Overdosing on caffeine as a deadline draws nearer.
** Recreational drugs in general, actually. The more intense a drug's effects are, the more likely it is to cause harm if not moderated, along with the need for more strict moderation. And the more intense effects you experience, the more curious you'll get for even stronger experiences. Though just because an experience is weak doesn't mean the damage is light: air duster as an extreme example. Alcohol is an aversion, though: drinking more after getting buzzed actually decreases the euphoria and eventually can cause severe depression and rage.
* There's a popular recipe among Russian students which consists of mixing 50 ml of Coke with 2 teaspoons of granulated coffee. Due to how it works on your body (Coke pretty much expands your blood vessels and makes caffeine go into the bloodstream much faster, multipliplying its effect), it can give you a huge energy boost for 8 to 14 hours. On the other side, even a single cup can have some harmful effects on your health, from high blood pressure to body tremors, not to mention that it's a guaranteed way to ruin your sleep schedule.
* Not exactly a technique, but human muscles are actually so strong that they can ''rip themselves off your bones''. Usually, the body has all kinds of limitations on itself to prevent it from happening, like pain. But in situations where super strength is the meaning of life or death (like being slowly crushed under some heavy boulder), the body can drop these limits by itself. It'll save your life when needed but at a really really painful cost. It will eventually heal, ''if'' you're able to find a doctor who can properly set your broken bones and muscles so that the ligaments and tendons heal naturally. And, also, you'll need to follow his protocols for recovery ''to the letter''.
* Steroids, blood doping, performance enhancing drugs and other methods are illegal in most official events, partly for this reason.
* Water methanol injection, also called as War Emergency Power, on turbocharged internal combustion engines. Injecting 1:1 water-methanol mixture to the combustion chamber can boost the performance of the engine for up to 33% and add up extra horsepowers. Unfortunately, it will also damage the cylinder heads. In WWII, its use was approved only for emergency situations, like an airplane escaping from a [[AcePilot particularly nasty enemy]], and using the mechanism involved on breaking the seals.
** Likewise nitrous oxide injection, called [[BilingualBonus ''Ha-Ha-Gerät'']] in the Luftwaffe. It will boost the performance, but long periods of use will seriously damage the engine.
** This is the effect of pushing the engine past its rated limits. What's on paper is what the manufacturer has safely determined the engine will go up to without dying sooner than how long it's expected to last. You could always push an engine harder, but doing so wears it out faster. Sometimes ''much'' faster, if the strain you put on the engine passes what its structural integrity can handle, causing it to tear itself apart or burst into flames.
** In modern military aircraft, afterburners can certainly count in some cases. The way they work is by taking raw jet fuel from your tanks, and spraying it directly into the VERY hot exhaust section of the engine. This in turn adds up to a sudden burst of power from the engine which will get your aircraft from just barely scratching the sound barrier, to moving twice the speed of sound in the span of a minute or so depending on the aircraft. This comes at a price however. Normally, afterburner use is relegated to take off, or on a bolter[[note]] When a naval aircraft misses all of the wires and needs the extra power to get back in the air[[/note]]. These short bursts normally don't do much damage to the engine, but using it too often (as in the case with most dogfights), can shorten the life span of your engine, meaning it'll have to be changed out once you return to base. However, use the afterburners too much, and you won't even have to worry about that, because your aircraft will eventually clunk into the ground with not even a drop of fuel left in the tanks.
* 'Cooking off' grenades involves pulling the pin and allowing it to tick closer to detonation before throwing it to the target. Successfully pulling it off results in the grenade exploding mid-air, showering the enemy with shrapnel while giving them less time (if any) to pick it up and throw it somewhere else. Failure results in the grenade exploding in your hand, which is unpleasant to say the least.
* Overclocking a PC's CPU can help squeeze in a performance boost, but this is not something to be done casually; without a good cooling system to offset the increased generation of heat, overclocking is a good way to ensure that you'll be shopping for a costly replacement CPU.
[[/folder]]

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