In How I Became Yours, as Azula is regaining her lightning bending powers, Mai takes the opportunity to throw a knife into her chest, which nearly kills her. This averts Talking Is a Free Action and shows that mundane weapons, even ones as seemingly unimpressive as knives, are a threat against benders.
Aang's sparing of Ozai put Zuko's legitimacy as Fire Lord into question and loses him the respect of his comrades, seeing they all told him to kill Ozai and he put his beliefs over the good of the world.
When Zuko is hit by lighting, he had to see a real doctor and was comatose for a few days and bedridden for a week afterwards.
Twice more in the prequel Jet's Troubling Obsession, when Zuko tries to show Jin the view of Ba Sing Se, she lacks the fitness and strength that most of the Avatar cast has and had to be assisted by Zuko to get on the roof. This was supposed to compare the cast to normal people. Also, Jet's therapy proves counterproductive because he doesn't believe he has a problem.
The Joker seemed satisfied, "NOW!" he clapped his hands together. "Where's ole little Griphook?" The tiny goblin stepped forward reluctantly, not pleased at all that "Harry" had remembered him.
In Here be Dragons the protagonist's mostly civilian crew tries to play Big Damn Heroes against an enemy powerful enough to capture two Jedi... and swiftly get their arses kicked, needing The Cavalry to save them in turn.
Mare Genius: Pinkie tries to surprise combat-trained Agatha with a Party Cannon and gets exactly the kind of counterattacking Reflexive Response you would expect from someone seeing what appears to be a weapon pointed at them.
Subverted in Mikami Vs. the Cybermen. After eight days straight of writing, he mentions how surprised he is that he hasn't run out of ink. Double Subverted right afterwards, when he dies of thirst.
Played with, though also straight, in the Nineteen Eighty Three Doomsday Stories, which has Austria hoping against hope that Hungary survived Doomsday. She doesn't. Though it doesn't stop her from looking after him even after death.
No Chance For Fate is built on this trope. Reality ensues hard on the common tropes of the Fuku Fic as well as on the source material of both series. Too many to list here. However, despite or maybe because of this, the story reads well.
In White Devil of the Moon, Nanoha realizes that Princess Serenity could have caused a diplomatic incident if she came to harm in any of her trips to Earth, and when she fell in love with Endymimon, he might have turned out to have been an unscrupulous individual seeking the throne.
In the Teen Titans fic Consequence of Misunderstandings, Starfire attacks Raven (who left the team five years prior) while the latter is on a date. Afterwards, not only does the Titans' reputation take a major blow, but the entire situation becomes an interstellar incident since Starfire is Empress of Tamaran. Batman lectures them after hearing "all the details about that debacle from various media sources. And from the Department of Justice. And the State Department, the Department of Defense, Homeland Security, and the leaders of the Armed Forces." Furthermore, the fact Starfire ordered three battlecruisers into Sol's heliosphere without informing the Justice League or the Armed Forces is treated as an act of war. She's given twenty-four hours to get them out of the system or they'll be destroyed and she'll be deported from the planet and barred from ever returning.
As demonstrated in Spira Mirabilis Light's desk trap involving an electric current that would ignite a plastic bag of gasoline is not a good idea and the way he has it set up it would blow up even quicker in real life. (By quicker we mean immediately. Gasoline melts plastic).
A Story of Stupid shows what would happen if someone recognized Light while he was out manipulating Naomi Misora. Also Sayu overheard her brother shouting at the television:
Sayu: Why is he screaming to the TV about justice? […] Wow. My brother's on crack.
In To Feel Alive Light misses the Lind L. Tailor broadcast entirely because the overworked honors student crashes in the middle of the afternoon. This is due to not drinking any coffee after he'd been awake for all the previous night attending cram school, killing criminals, and talking to Ryuk.
River faces off against a rival pirate crew's Arrogant Kung-Fu Guy. The battle begins with them sizing each other up, and with the martial artist declaring River as a Worthy Opponent, who might be able to truly test his skills, and he rushes at her with his bo staff. River shoots him twice in the head. Then she demands chocolate.
Later on, River is facing a group of vengeful pirates. She's on the ground, and they're in their ship. She starts running for cover behind some boulders where they can't shoot her, only to get hit by the backwash of their engines and get thrown into said boulders, breaking her legs and back.
In Frozen Hearts, when pretending to be ice harvesters, Hans and Heins end up making some amateur mistakes, one of which results in an accident that almost gets Heins killed and is decidedly not Played for Laughs. They have a harder time pretending to be a profession than most fictional characters.
Boys Und Sensha-do, found here has "simunitions" for the tanks in tankery, as the author believes tankery is otherwise dangerous enough. Despite this, Miho ends up being seriously hurt when she accidentally gets hit in the chest by a shell, and would have lost her legs if the tank had accidentally rolled over her.
Many Harry Potter stories have Hermione and/or Harry realize they're stuck in the magical world when they graduate Hogwarts unless they get several years of tutoring. Learning magic is great and all, but they have no muggle education past primary school.
One fanfic shows that having a potions class with no safety instructions and students throwing random ingredients in each other's cauldrons does not a safe enviroment make. As a result, Snape is sent to Azkaban for the scores of health issues his teaching has caused including almost a dozen students being rendered sterile (a VERY large offense in a world that puts a so much emphasis on bloodlines).
The Boy Who Died shows the consequences of making little Harry Potter a famous figure, icon of the Light, and the enemy of dark wizards everywhere before he even knows how to talk let alone protect himself.
In Changes Dumbeldore's excuse of "I know what's best" doesn't cut it in a court of law and when his history of child neglect comes to light he is stripped from his position as a school headmaster.
In Harry Potter: Junior Inquisitor, when Amelia Bones finds one of her aurors (Tonks) sneaking into a restricted area on Dumbledore's orders, she fires Tonks on the spot. "Leader of the Light" or not, aurors aren't allowed to take orders from anyone outside the chain of command.
From the same story, Harry later learns that his Firebolt was destroyed beyond repair while being checked for curses and the professors covered it up by buying a new one with his money. It's noted by Susan and Amelia Bones that it'd take longer for the manufacturer to repair it or build a new one than the amount of time the teacher's allegedly took to fully strip it down, check it for curses, and rebuild it.
If Thems The Rules shows regardless of Harry raising Tom Riddle in better circumstances and giving him an ideal childhood, Tom Riddle is still a sociopath.
In Lord of Caer Azkaban Harry sends in his elite team of soldiers to take out Voldemort and his Death Eaters. Harry doesn't participate in the battle himself because he knows that, as an untrained student, he'll just get in their way.
A Necessary Gift shows that even if you defeat the Big Bad that doesn't mean everything gets magically better or his followers (and the prejudiced ideology he espoused that allowed him to gain power in the first place) will go away. In fact things get worse because the only one who could control the psychos is no longer around...
As mentioned in an author's note in the AURaised By Darkness concerning why Sirius Black isn't immediately released from Azkaban; because although Minister Fudge has grown a backbone in this fic and "is being nice to Harry and the Dementors he has no evidence to suggest Sirius Black is innocent and he still wouldn't believe Harry who is close friends with the man."
In Temptations of a Dark Soul as soon as Harry begins to act independently (and against Dumbledore's wishes) Dumbledore has his Gringott's accounts frozen and sends the Order of the Phoenix and nasty Special Forces guys out to retrieve him.
Wish Carefully illustrates the logical consequences of the Death Eaters winning the war: it turns that the Light lost to them on purpose, because they exiled all Light supporters and muggleborn they have no economy or people to lord over and Dark wizards tend to be the very bottom or very top of society. Their society is slowly dying off due to frequent inbreeding and social mores preventing large families.
You're on my side? shows the logical conclusion of leaving little Harry Potter with so-called guardians who hate him and don't care if he lives or dies.
This trope is the entire premise of An Alternate Keitaro Urashima. Keitaro refuses to run the Hinata Inn since, not only are several of the girls violent and don't want him there, he's got his own life to live and can't devote that kinda time to running the dorm. When Granny Hina tries to play the childhoodpromise card, Keitaro points out that you can hardly expect someone to stick by a promise they made when they were five. And finally, Naru's and Motoko's chronic violence comes back to bite them both. Naru is treated as a pariah after several students see her punch out Keitaro while he's talking to Mutsumi. And Motoko is arrested for assault with a deadly weapon when she attacks Keitaro with her katana.
Kaolla Su in For His Own Sake decides to "cheer up" the guests at an inn by chasing them with exploding Mecha-tamas. Dozens are injured, the inn is nearly destroyed, and Kaolla is arrested as a terrorist.
Meanwhile, Naru's Hair-Trigger Temper gets her into some very hot water when she punches a man that she assumed was making creepy passes at a woman. The man and woman are revealed to be a married couple and on top of that, he's revealed to be the career adviser at Tokyo University Naru had an appointment with, meaning Naru essentially put her academic future and job prospects in jeopardy.
Love Hina: Like It Could Have Been loves this trope. When the girls angrily declare that they'd never let a man be their manager, Keitaro leaves, having compromised with his parents (and thus not being forced to live at the Hinata Sou). Later Kitsune is told to either pay her rent by the end of the month or find a new place to live, and both Motoko and Naru are smart enough to rein in their hatred of men so carpenters can fix the damage Su's inventions have caused.
In Oneesama, Shizuru giving a Skinship Grope to Natsuki is treated as sexual harassment by Miss Maria, who says Shizuru could be expelled if she felt it necessary. Thankfully, she's also a Reasonable Authority Figure, and decides on a punishment that forces Shizuru to humble herself and approach Natsuki as herself, rather than her persona as top Coral.
In Perfection Is Overrated, a handgun is significantly less powerful than most of the Himes' Elements or Childs, but it still has enough power to kill someone. Shizune, whose special ability made those of the Himes useless finds this out the hard way.
In Renegade ReinterpretationsHumans do NOT magically Advance Swiftly. As such, when the Batarians come visiting, they get Curb Stomped over and over again and only Zerg Rushing enables them to desperately throw lives for time in the hope of being able to turn the tide someday. After they do so, the cultural scars of the generations-long war means that mankind does not magically become receptive to further alien contact.
The Equestrian Civil Service Series is all about this. In a realm of gods, monsters, heroes, epic adventures (and Royal Brats), there still needs to be somepony to run things behind the scenes, leaving the eternally Beleaguered Bureaucrats to deal with everything from imminent disaster to the fallout of a visiting celebrity to a castle covered in custard.
The Finger Trap has Twilight Sparkle appear on humanity-occupied earth, and go to the first house she can see to ask for directions. Instead of a person who sympathizes with her and wants to be friends, the main character is the one contacted... who distracts her long enough to call Animal Control.
In Self-Insert FicAberrationOccidental Otaku Rae trips into a portal and is transported in Konoha. Does she learn cool jutsu, gain a bloodline or take a level in badass? Nope. She is stuck homeless in a world alone with nothing but her clothes on her back, will never see her family and friends again and is unable to learn any jutsu because she's from another world and doesn't have chakra.
As Destiny Is A Hazy Thing shows, an invasion that severely weakens two of the five great villages when all villages are in a constant Cold War is liable to set off the next World War.
The Sasuke retrieval mission was a success, although Naruto lost his right arm (worry not, for it grew back). Sasuke, however, is charged with treason and locked up in ANBU prison with his ninja status (his charka network is also shutdown) revoked without any chance to regain it or any parole. Made worse due to attacking Naruto, a fellow Leaf nin, and placing the others on the mission in danger. Naruto himself doesn't dispute the punishment.
After years of dealing with Sakura (who'd commit Domestic Abuse on him at any time or call him an idiot or a perv), 13 year old Naruto has the notion that ALL women will beat him for anything even something out of his control leading to a rather OOC (read: quiet) Naruto on a trip with Tsunade, Shizune and Hinata and a case of accidental Covert Pervert. Tsunade sits him down and tells him "No. Sakura just had issues. We are not going to beat you for something as stupid that."
Naruto:Asunder shows that Offscreen Inertia is fully in play when Naruto and Hinata leave the village for training. They come back a week later and Konoha is in ruins courtesy of the Akatsuki.
Tsunade snaps at Jiraiya saying that since Naruto came back (from the 3 year training trip), he's been in fights with S-class nin after S-class nin. Jiraiya says it will make him stronger. Tsunade says he's more likely to die. Guess who was right.
In The Scorned Son, the Wave mission is a failure because teamwork or not, three ninja barely out of the academy don't really have a chance against a Jounin that's trying to kill them for real. The end result: Kakashi is dead and Kiba nearly kills himself keeping Sakura and Naruto alive long enough to find help.
In Marie D Suesse And The Mystery New Pirate Age, the eponymous character ends up in quite a bit of trouble when she lands in the One Piece world, looking exactly like the Queen of the Pirates and lacking any significant combat abilities. This goes to show that being thrust into your favorite fictional world is not everything it's cracked up to be.
In It's a Wonderfully Splendid Magnificent Life, while Tamaki is viewing his life if he'd never left France, what finally convinces him to keep things the way they are is seeing him and his mother living in poverty, with him struggling to pay her expenses. What really makes this a Reality Ensues moment is that being together as mother and son does not make up for this for either of them, in stark contrast to many works that would indicate that being together as a family is most important.
In Like No One Ever Was, one of Pikachu's Thunderbolts ends up getting Ash hospitalized and possibly permanently ending his trainer career with Ash suffering from major internal damage and brain injuries. Apparently even before that fateful Thunderbolt, Pikachu's friendly shocking of Ash has slowly deteriorated his muscles, meaning his journey would have been coming to an end anyways. Pikachu is horrified when he learns of this.
Multiple hotspots of 18,000F heat will cause terrible environmental damage.
Olympus Mons fighting will result in severe and permanent environmental damage.
Mass panics can be just as dangerous as the disaster itself.
In The Sun Soul, a(n insane) bug catcher pulls out a knife that was stabbed into his leg. Blood starts gushing out immediately, since the blade had sliced the femoral artery. The only thing that stopped him from dying from blood loss was the Weedle got to him first.
In Innocence, Misty confessed her feelings to Ash in the backstory. This nearly broke their relationship apart as Ash, being a ten-year old Chaste Hero, had no idea how to respond.
Cilan in Identity Crisis who along with his brothers, turn out to be a part of the Shadow Triad and The Mole is torn between the people he genuinely became friends with or his brothers and his organization. Does he pick a side and affirm his loyalty to them? Nope. His wavering loyalty cost him his relationship on both sides as his brothers no longer trust him as he's not truly committed to their cause and his friends are angry that he wasn't really their friend and initially intended to backstab them.
What does Issa do when his daughters start defying him in Here In My Arms? He withdraws their tuition from Youkai Academy so they have to come home. Tsukune even laments that for all the power he's gained, he still can't protect them from everything. Averted however when his familiar gives away a gem made from her fire to pay for their tuition.
The second act of Imperfect Metamorphosis begins with (almost all of) the most powerful residents of Gensokyo meeting in order to fight a powerful new threat together, a common Fandom Specific Plot for Touhou fics. Turns out that a bunch of distrustful, violent megalomaniacs don't make the best alliances, and a combination of differing priorities, politics, and centuries-old grudges cause the union to fall apart before it began, the various factions and sub-factions either leaving or starting their own schemes.
Yukari assembles a dysfunctionalRagtag Bunch of Misfits, uniting them against a powerful enemy with massive odds stacked against them. They lose, horribly. Turns out going against a freaking Outer God was not her wisest course of action.
Braid of the Limbo Clone Squad. When he was facing his demise he was plucked from his universe by a mischief god and given his choice of powers. His choice: the natural laws of his Earth will always rule him. How does this count as a power? Well, the universe he was thrown into is an anime universe, meaning that the only reason the heroes haven't died is that the universe's laws seem to want to protect them. Which means he can see through the flimsy disguises that most people use and has no problem just killing the fuckers when they're not powered up with a simple sniper shot to the head.