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- Moldiver is a rare example of a time limit that isn't a round hour, or even a round minute. It's still meaningful, though: 666 seconds.
- The Evas in Neon Genesis Evangelion technically have exact-time battery limits depending on power usage, but are usually conveniently vague about said usage. Evas can fight much longer while still attached to an umbilical power cord, but they're less agile and much less cool-looking when doing so.
- Not that running out of power ever particularly hinders them. Shinji is the one who tends to run out of power, but he also tends to go berserk and kill the Monster of the Week regardless. Asuka is not so lucky.
- Considering why exactly Eva-01 is able to outperform Eva-02 in Berserk Mode is not astonishing, if you understood whose soul resides in it...and that person may be the primary player in the series' massively complex and confusing conspiracies
- Not that running out of power ever particularly hinders them. Shinji is the one who tends to run out of power, but he also tends to go berserk and kill the Monster of the Week regardless. Asuka is not so lucky.
- All the Visoreds have time limits for their masks. Two are confirmed to be able to hold it for three minutes although it's implied this is the approximate time limit for all the Visoreds with the exception of Mashiro who can hold her mask for 15 hours and for unknown reasons has always been able to do so. They trained Ichigo to be able to hold his mask for 11 seconds. Protecting Orihime and Nel from Grimmjow is what allowed Ichigo to break the 11 second barrier and develop the ability to use the mask indefinitely. And to immediately regenerate the mask when it breaks. He's the only Visored who was capable of out-growing this trope. This is because Ichigo got his Hollow powers in a different way. He's not a Shinigami who was later infected with Hollow powers, but a Shinigami who was born with them.
- Prior to the time-skip, Hitsugaya's Bankai Daiguren Hyorinmaru could only be maintained for a set period of time before dissipating. His Bankai activated with three four-petal ice-flowers that hovered behind him. As time passed, the petals disintegrated, one at a time like a clock ticking down. When the last petal shattered, his Bankai disappeared. This was explained as his power being youthful and immature so he wasn't fighting with a completed Bankai.
- Downplayed, the petals only appear when there is no water in the area. If there is water, the Bankai can repair itself. And following the 18 month timeskip, he's mastered his Bankai sufficiently that the time limit never applies anymore.
- Yhwach can only leave his territory for an unspecified amount of time and is forced to retreat when Aizen slightly messed with his perception of time to make him think he had more time left. Energy seems to start bleeding off him when he hits the limit. He later gets around this restriction by transporting everybody into his realm.
- In One Piece, the effects of Chopper's Rumble Ball last for exactly three minutes. He can try it a second time if the fight lasts longer than that, but he loses control of his transformations if he tries, leaving him with no choice but to randomly transform and hope he gets what he needs. And if he goes for a third, well... things just get bad.
- Luffy's Gear Third has a variation of this. While there's no set amount of time it lasts, when Luffy stops the technique, he changes into a chibi version of himself that's pretty much useless in combat; he stays this way for an amount of time equal to that he had just spent using Gear Third.
- Luffy's Fourth Gear plays this straight. Maintaining it is such a strain that it automatically deactivates after a short time, leaving Luffy so drained that he can barely fight afterwards.
- Ban Mido of Get Backers can cause a person to hallucinate for exactly one minute (real time). He nearly always greets a person coming out of a hallucination with, "Exactly one minute. Have any bad dreams?"
- Tekkaman Blade turns into a mindless, berserk killing machine if he remains in Tekkaman form for thirty minutes.
- In Tokyo Mew Mew, Alto, actually Ryou in cat form, can only remain as a cat for fifteen minutes or get stuck like that forever.
- Numerous examples in Dragon Ball and its various sequels/movies.
- Oolong has shapeshifting powers that only work for five minutes before he changes to his default form. This is because he was kicked out of shapeshifting school before he could learn how to shift indefinitely.
- Freeza's 100% form is a beefed up version of his final form, but since Freeza almost never uses the form, he has zero stamina and burns out all his energy in five minutes. In Dragon Ball Z: Resurrection ‘F’, his new Golden form has the exact same problem, ironically after he had supposedly learned his lesson from his previous failure.
- The Fusion Dance introduced in the Buu arc allows two characters to fuse into a composite being with the powers of both, but only for thirty minutes before the technique ends and they split apart. If the beings are particularly powerful, it shorts out even sooner. In GT, for example, the fusion of Super Saiyajin 4 Goku and Vegeta, Gogeta, is so immensely powerful that he defuses after only ten minutes.
- The dead can be given permission to return to the world of the living, but only for a day. Like fusion above, a powerful character like Goku has even less time if he engages in prolonged fighting. What should have been a day was half that because used up all his energy fighting as a Super Saiyajin 3, forcing him to return early.
- Speaking of which, when he's alive Goku's Super Saiyajin 3 form sorta falls under this trope. Unlike the SSJ1 and SSJ2 forms, SSJ3 burns through Goku's energy reserves at a considerable rate, and eventually his power level starts dropping if he stays in it for too long. It gives him an absolutely massive power boost, but it's mainly meant to quickly overpower and dispatch foes that are stronger than SSJ2, but markedly weaker than SSJ3, before his energy reserves have enough time to dip too low. If SSJ3 Goku is in a fight against someone close to his power, and they end up lasting long enough against him for that to happen (such as his fight against Kid Buu), he can end up in serious trouble. However, it's hinted that this limitation happened because Goku wasn't used to having a living body after being dead for seven years, which wasn't as durable and didn't have endless energy like his dead body.
- The Super Saiyajin God form in Dragon Ball Z: Battle of Gods turns a regular Saiyajin into a God, but only for a few minutes. However, in Dragon Ball Z: Resurrection ‘F’, the Super Saiyajin God Super Saiyajin transformation appears to be a hybrized version of the God and normal Super Saiyajin forms that does not share that weakness.
- The Japanese anime version of Teenage Mutant Ninja Turtles has the title turtles able to transform into super versions of themselves, but only for three minutes.
- In the Pokémon Special manga, Mewtwo could only fight for three minutes at a time after he was caught by Blaine, thanks to some trouble with his cloning involving some Applied Phlebotinum and Blaine's cells. Any longer risks Blaine's life and tires Mewtwo out considerably.
- Yellow has a good number of powers, including heightening her Pokemon's level to a frightening point when under emotional stress. Using these powers, however, eats at her stamina like nothing else, and when she uses them too much, she falls into a sleep that cannot be externally disrupted no matter how inopportune the following situation.
- In the games, Regigigas is an inversion. Only 11 other Pokemon meet or exceed its 680 base stat total, and only two exceed its base Attack, but it has to suffer 5 turns of weakness to get the benefits.
- Can be negated entirely through the use of Gastro Acid, a move that disables a Pokémon's ability (which, as it turns out is what limits Regigigas).
- Mobile Suit Gundam 00 has the TransAm system which, when activated, makes the Gundams turn red and go three times faster for a limited time. Afterwards, they operate at reduced power for some time (since TransAm releases all the stored power at once and it takes a while to build the stores back up). It's worse for the false GN Drive mecha in the second season, since they lack the power output and using TransAm shuts it down completely afterwards.
- In Naruto, Danzo has multiple stolen Sharingans embedded in his left arm. Using a technique called "Izanagi", he had 60 seconds of being completely unkillable for each eye he had, and he had 10 extra eyes, so this extended to a total of 10 minutes. He was ultimately beaten by getting his perception of time slowed down by a second.
- In truth, this battle strategy wasn't as practical as it was convenient. With most fights in the series being chaotic brawls, anything could have happened to cause Danzo to lose track of the time he had for each eye, and he had to keep checking the eyes like a watch in the middle of his fight with one of the most dangerous ninjas in the series.
- Madara also displayed this technique in Chapter 510. He claimed it was a "Perfect" version of the technique, but the only difference seems to have been that it lasts several minutes longer.
- Sage Mode uses up a lot of energy and can only be recharged by standing perfectly still, so it wears off quickly in battle. Naruto gets around this restriction by using his shadow clones to recharge for him.
- This seemed to be more because Naruto's jutsu took a considerable amount of chakra to use: At one point he thought to himself about having enough "nature chakra" for another Rasenshuriken, having already used one to destroy one of the Six Paths or Pain, after crushing another with a Rasengan, crushing summons with giant Rasengans, and another path with a dual Rasengan. In total, it's implied he only had enough to use the Rasenshuriken four times.
- Later on, he manages to greatly surpass this limitation by throwing 5 Rasenshurikens in rapid succession before collapsing, and in another instance he creates a Rasenshuriken several times his size with the destructive power of a Bijuu-dama and still has enough sage chakra to fight.
- Naruto's full-on Bijuu Mode only allows him 10 minutes at most to fight before it dissipates. This is because Naruto hasn't perfected it compared to Bee, who can stay in his Bijuu Mode for almost an entire day. After receiving Hagoromo's power, he can maintain an upgraded version of this form indefinitely and put out near-unlimited amounts of chakra.
- Tobi's/Obito's Kamui technique makes him intangible for only about 5 minutes, which is a weakness that Konan exploited.
- The deceased Obito transfers his spirit into Kakashi to give the latter his full Sharingan abilities, but it can only be maintained for a limited amount of time before having to return to the other world.
- In Freezing, the girls' superpowered, armored "Pandora" mode has a limit of three minutes, after which they can no longer fight for quite some time, meaning that this is a last resort only.
- Subverted in Super Dreadnought Girl 4946. Mana is told that it's okay to eat Tobita for a power boost as long as she spits him up within three minutes. In reality Tobita should have died the moment Mana swallowed him, and the three minute rule was a lie to convince Mana that she wasn't killing her boyfriend. The fact that Tobita actually survived was a surprise to everyone except Mana, and ever since then they kept the three minute rule simply because they have no idea about how long he can ACTUALLY survive.
- In A Certain Magical Index, Accelerator gains this limitation after his Heel–Face Turn. Originally, he could use his Story-Breaker Power to change physical vectors as often as he wanted, with no real limitations. Later, however, he can only use it for up to thirty minutes, and relies on a vulnerable transmitter to do it. He later manages to improve the device and make it more energy efficient.
- The powerful mage Cendrillon automatically loses her powers at midnight or sunrise, similar to her namesake: Cinderella. Unfortunately for her, she will also lose her powers if midnight or sunrise is simulated.
- Wild Tiger's Super Strength in Tiger & Bunny has a 5-minute time limit per activation, as does that of his partner, Barnaby. Midway through the series his powers get stronger but shorter lasting, whittling down to four minutes by the series finale episode, and one minute by the Where Are They Now epilogue with it looking quite likely he'll lose them forever. Unless there's another season, of course.
- Rurouni Kenshin: Shishio Makoto was once burned alive, damaging most of his sweat glands. As a result, he cannot fight for more then fifteen minutes, at which point he overheats and dies. In the final showdown, he goes over this limit and literally goes up in flames.
- Rosario + Vampire: Whenever Tsukune got injured, Moka would inject him with her blood to heal him. At first, this would grant him temporary vampire powers as a side effect. After awhile it gets subverted, because the blood starts to take a toll on his body, and the transformation becomes permanent, with consequences. He recovers somehow and keeps the powers, so this trope becomes redundant.
- Although, he's still at risk if his limiter is ever broken.
- Cure Ace of Doki Doki Pretty Cure can only stay transformed for no more than 300 seconds. She's also the only Cure from the franchise who transforms from a kid into a late teen/adult.
- The Newtype-Destroyer (NT-D) Mode in Mobile Suit Gundam Unicorn last for 5 minutes when activated to prevent the pliot from getting overwhelmed, but is enough to curb stomp every mobile suit in sight.
- Ryuko Matoi's Kamui Senketsu in Kill la Kill initially has this limitation. Due to continuously feeding on her blood, extended use involves the risk of her passing out for blood loss. However, this issue is solved once both realize her embarrassment and rejection of Senketsu's skimpy gear was the problem. Once she accepts Senketsu, the issue is resolved. On the other hand, it's hinted that Satsuki's Junketsu has an unspecified time limit — after a prolonged battle, it begins attacking and has to be tranquilized for safe removal.
- In My Hero Academia, All Might can only tap into his powers for a few hours due to an injury he sustained long ago, a secret known only by the main character and a few trusted comrades. When unpowered, he goes from a towering wall of muscle to an emaciated skeletal figure constantly coughing up blood. After passing on his Quirk to Midoriya, his time limit gradually gets shorter and shorter. All Might knows it won't be long before his power vanishes for good.
- Yu-Gi-Oh! GX: The Contact Fusion forms of Neos can only last for one turn and then they go back to the Fusion Deck (before the term Extra Deck was invented). To avoid this weakness, Judai has cards like Neo Space or Instant Neo-Space to not keep them on his field.
- Yu-Gi-Oh! 5D's: The Saviour (or Saver forms of Stardust Dragon and Red Daemon's Dragon can only last for one turn and then they go back to the Extra Deck, but unlike Neos, their original forms do come back on the field. But since they are so powerful, they usually win the duel during the turn they are summoned, it only happens once during the entire series.
- As his name implies, Hourman's Super Serum only lasts for an hour; he uses the phrase "Hour of Power" quite often too. The villain Per Degaton, who can accelerate time, is naturally a Man of Kryptonite for him.
- The second Hourman Rick Tyler also had the ability to spend an hour in a timeless dimension with his father. This eventually ended when Rick was mortally wounded, and all the time was used up to save his life. The android eventually gave his life in Zero Hour instead of Rex Tyler, enabling father and son to return home.
- Android Hourman also had an Hour of Power, which gave him access to all sorts of cool time-manipulation abilities (just about the only thing he couldn't do was make his Power Hour last longer than 60 minutes.) This was actually a self imposed condition, prior to that he had continuous access to his powers. He limited himself to explore his humanity.
- The Green Lantern rings used to require charging every 24 hours, but this has gradually been changed to more closely follow a "battery" model, where the charge depletion depends on the use of the ring.
- The Doom Patrol's Negative Man could separate his energy form from his body for 60 seconds at a time. He had to act fast; If he didn't return to his body in time, he would die.
- In one Thor story, his power had been halved, and a villain was beating the living daylights out of him. As a test, Odin granted Thor his full power for thirty seconds. Thor won. (Do not screw with someone whose titles include "god", no matter what they are the god of. If they're the god of something like "thunder" or "storms", don't even think it.)
- Originally, if Thor lost contact with his hammer for more than 60 seconds, he would change back to his human form. This limitation has since been removed, although it made a comeback when Eric Masterson, otherwise a normal human, became a replacement Thor by taking up the hammer.
- According to one X-Men source Rogue's power drain ability (in the comics) tends to last for about a 1:60 ratio—that is, for every second she holds it, she has what she took for 60 seconds. Life Energy and memories may work on a different scale, of course, and since it's possible for her to take powers permanently, this ratio breaks down the longer she holds on, but, well, A Wizard Did It.
- It was later revealed that the limits to her powers were psychological, not physical. After she was "reset" and her trauma-induced mental blocks restored, she could call up any previous power or memory she had absorbed at will, as well as be able to touch someone without draining them. That said, the 1:60 ratio was rarely outright stated to begin with, and it's very possible that later writers ever heard of it, so it's more likely just a non-definite exponential ratio.
- J2 of Marvel Comics 2 has a time limit on his transformed state that gradually gets shorter as his body matures and becomes better at using his powers.
- All-Star Superman has a formula that gives whoever drinks it Kryptonian superpowers for 24 hours. When Lex Luthor takes it, Superman uses a gravity gun to increase Luthor's personal gravity 500 times - which only manages to slow him down temporarily. Thanks to General Relativity, the gun also makes 'Luthor's' 24 hours run down a lot faster and his powers give out before he can finish Superman off.
- This is based on old devices Superman had in the Silver Age which could do the same.
- The H-Dials from the 1980s iteration of Dial H For Hero had a set hour time limit for the superheroic identities they bestowed upon the wearers, as well as an hour wait before the dialer could transform again (which was imposed whether the dialer used the previous transformation for the full hour, or voluntarily reverted before their hour was up). However, it was found in the final story arc that the H-Dials could be immediately passed onto another person (as long as that person hadn't used one within the last hour) to circumvent the limitation.
- Darkman, as opposed to Ultraman, needs to get out of light within 99 minutes. After that, the synthetic skin he uses for his masks dissolves.
- The Animorphs had two hours before they had to "demorph" into human form, or else be stuck as an animal. Used as a major part of the plot (one of the main characters was stuck from the beginning of the series), but suffered somewhat from a Two of Your Earth Minutes Running Gag. It also appears possible for someone with high willpower to demorph just beyond the time limit, but with greater difficulty. Note: There are instances in which the time limit can be reset. One book has Cassie get trapped as a caterpillar, but her natural transformation into a butterfly resets the clock. Also, the Ellimist has the power to restore someone's morphing ability after they have been mode locked.
- Inverted in ''The Stormlight Archive; by Brandon Sanderson. Shardblades can be summoned out of thin air, but it always takes ten of the owner's heartbeats to do it (meaning you get it faster if you're adrenaline rushing, nice feature for a weapon). In this case, it's not an exact time until the power ends, but an exact time until the power begins.
- The Animorphs television series has the extreme Exact Time to Failure version: Ax is close to being trapped in human form, counts down the last few seconds to a nearby teammate, but is finally able to get away and has none of the difficulty changing back that the book versions had when cutting it close. This would suggest that changing back after 1 hour, 59 minutes, and 59 seconds is no different from changing back after five minutes, but changing back at 2:00:00 is completely impossible.
- Basically, the overwhelming majority of giant hero series have the three minute rule, because the Ultra Series writers worked on most even if the series is not officially an Ultraman series. Either the chest or the helmet will always have the light that lets him know when time is short.
- Ultraman popularized this trope for live-action Japanese superheroes. His Bizarre Alien Biology makes the atmosphere harmful to him, but — depending on the iteration — he stores solar energy for three minutes, often marked with a "color timer" on his chest that goes from blue to blinking red as this runs out. Just about the right amount of time for an easily-budgeted Monster of the Week fight sequence in a 24 minute show...
- ...And then you have Ultra Seven, who doesn't seem to have this limit.
- From the same studio there's also Fireman, who cannot stay in his Agan form for more than 3 minutes due to sunlight being harmful to Agans.
- Denkou Choujin Gridman: Gridman is really hard on the computer that hosts him; three minutes is the limit before Explosive Overclocking takes place.
- Iron King is water-powered and burns through his supply in three minutes, demorphing.
- There's the '70s superhero Kaiketsu Zubat, who explodes if he wears the Zubat suit for more than 5 minutes. Justified in-show as being a Super Prototype, finished by the guy himself even though it's out of his field. Worse, the time spent catching up with the villain counts (compare to the Ultras, who can extend their time by conserving power or shorten it by using too much at once. Three minutes sitting in a comfy chair, if you had one big enough, wouldn't be the same as three minutes of battle; not so Zubat.) so he barely has enough time before the indicator on his helmet makes a full rotation and his visor opens, signifying the shutdown that prevents "kaboom".
- The Makai Knights of GARO have exactly 99.9 seconds to fight in their armored forms before it runs out. They can choose to exceed the time limit if they want, but the results are... not pleasant.
- A version of this occurs in Stargate SG-1, where barring some Applied Phlebotinum (and for this show exceedingly rare applied phlebotinum — perhaps three or four times in the entire series), no artificial wormhole (i.e. Stargate connection) can be maintained for more than 38 minutes and a few seconds.
However, the show never seems to treat this as a hard and exact deadline. It seems 38 minutes is a rule of thumb and that there may be a small variance each time (for instance, they usually compare the current time to the longest recorded time a gate has been been open in the past rather then to a hard deadline). Combine this with the very random length of time the gate can stay open and the gate deadline starts to feels more like a natural limitation of a gates energy capacity and reliable failsafe systems and less like a contrived exact time limit.
- Power Rangers/Super Sentai:
- Silver Ranger/Megasilver from Power Rangers in Space/Denji Sentai Megaranger had a transformation time limit of 2.5 minutes. And then he got over it when the bad guys tried to exploit this. With lots and lots of research.
- The Storm Megazord/Senpuujin in Power Rangers Ninja Storm/Ninpuu Sentai Hurricaneger had a special form that lasted 1 minute before switching back (although as the series went on it went transformed for about 2 mins).
- The Engines from Engine Sentai Go-onger can maintain their large forms in our universe for 10 minutes before rusting.
- In Power Rangers S.P.D., Kat was given an expendable morpher for one episode to help her team which would only work for one hour.
- In Tokumei Sentai Go-Busters, there's an indicator of how much of the superfuel "enetron" is being burned. When it comes to finishing a fight, faster is better, though they've got way more time than many of the other Toku examples on this list.
- In Power Rangers Dino Charge/Zyuden Sentai Kyoryuger, each Ranger carries a set of three or four batteries (called Dino Chargers in the former and Zyudenchi, or "Beast Batteries", in the latter) that have a number of uses, but could only be used once before needing to be recharged. If a Ranger transforms, summons a weapon, uses a Finishing Move, and summons their mecha in quick succession, then that's pretty much all their batteries drained and they're stuck for a while.
- Faiz Axel Form in Kamen Rider Faiz only worked for 10 seconds before shutting down. While this seems short compared to some of the other examples on this page, keep in mind that this is 10 seconds of Super Speed.
- Metroid Prime 3: Corruption has Samus' Hypermode, which actually has two timers: 10 seconds after activation, the Hypermode turns into Corruption, causing the meter to rise over time (as does being hit by certain attacks), and 25 seconds after activation, the mode is automatically turned off. To be fair, the second time limit actually makes sense as an internal safety measure of her PED suit.
- A number of powersets in City of Heroes have abilities along this line. The best example is probably the defensive powersets which frequently include an "uber-mode" power that renders the character nearly invulnerable for a few minutes but has a very long recharge time.
- Any temporary invincibility power up
- Several units in Super Robot Wars have command Super Modes that last for a limited number of turns. By the endgame, most of such limitations are removed and become straight Mid-season Upgrades.
- The Gran Kaiser combines with its supporting mecha and forms the titular Gravion; unlocking new attacks along with five subpilots.
- The Unicorn Gundam transforms into Destroy Mode, boosting stats and unlocking its strongest attack. Unusually for the series, the turn limit isn't removed in Jigoku-hen, meaning Banagher gets stuck in the sidelines for the endgame.
- In Kid Icarus: Uprising, Pit can't fly despite being an angel. At the start of every level Palutena grants him the Power of Flight, which allows him to fly at very high speed and boosts his attack power. These segments make up the Rail Shooter portion of the game. However, it only lasts for about five minutes and it needs time to recharge. Breaking the time limit or using it back to back will cause Pit's wings to catch fire. There's several parts of the game where they have to watch the clock and find somewhere to land quickly, and near the end Pit overuses it to save Dark Pit and nearly dies.
- At the Whateley Academy in the Whateley Universe, Dash has super-speed, super-strength, and Nigh-Invulnerability. But it looks like he only has it for a matter of minutes, and can't call it up without a lot of effort ahead of time.
- Word of God finally explained it: Dash is some kind of Energizer and can focus to make his body stronger and tougher and faster, but it only holds up for ten minutes or so, and it takes about that long for him to power up. After, he needs hours before he can do it again.
- Many of the SCP Foundation artifacts have specific hard time limits, although the round units are generally averted. For example, SCP-431-ARC sets its wearer on fire after 22 hours and 17 minutes of being worn.
- The Omnitrix of Ben 10 has a time limit that is supposed to be ten minutes Earth time, but in practice differs from use to use. In the original series, it lasted ten minutes, and took ten minutes to recharge, and there's no switching forms or demorphing before those minutes are up. The rules change in later series; usually, the more time he has, the less control he has of the other aspects of how it works; currently, in Omniverse, the time limit is very random; we've had him change, try to fight, but immediately change back before he can make a move; we've had him stay in one form for half an episode. He's also got little to no control over which alien form he gets. The up side is that when the Omnitrix does time out, it's always ready to go again in under a minute. It's revealed that the time limit and the way the rules of how the thing works can change are due to Ben's own inexperience with the device: Elseworlds and Time Travel episodes have given us a glimpse of adult Ben, and "Ben 10,000" does not suffer from a time limit, or any of the Omnitrix's other limitations. Every so often, present Ben's Omnitrix has "Master Control" activated and gains full control, but Status Quo Is God; he only gets Master Control on rare occasion, and he never gets to keep it longer than the climax of the episode in which it happens.
- Roger Ramjet's proton pills gave him "the power of twenty atom bombs for twenty seconds".
- Superboy of Young Justice normally has Super Strength, Super Toughness, Super Senses, and super-leaping abilities due to being a half-human clone of Superman. In the episode "Agendas", Lex Luthor who is the donor of Superboy's human DNA gives Superboy patches called Shields. When Superboy uses one, it suppresses his human DNA, which grants him the rest of Superman's powers (Flight, Heat Vision, more Super Strength) for one hour. However, it also fills Superboy with rage.
- In Avatar: The Last Airbender, Sozin's Comet grants firebenders incredible power: the first time they used it, they managed to commit near-total genocide on the Air Nomads, with the protagonist being the only survivor, and that's arguably because he was frozen in an iceberg when it happened. The second time it comes, Phoenix King Ozai plans to use it to burn down the Earth Kingdom; from what we saw, given how much power the Comet granted, he might have pulled it off. However, it's not clear how long the Comet's effects remain, with guesses ranging from a few hours to a few days.