* In ''Webcomic/SluggyFreelance'', when Torg [[http://www.sluggy.com/daily.php?date=990228 exorcises the demon K'Z'K out of Gwynn]], he sets K'Z'K free upon the world. Subverted in that this was actually intentional: they needed the Demon out of Gwynn so that they could use their plan on it directly and not harm her. However...
** Done again almost immediately afterwards, [[spoiler: when Riff's attempt to freeze the demon in time actually sends it ''back'' in time, creating all sorts of havoc during the middle ages]].
* In ''Webcomic/TheOrderOfTheStick'', after defeating Xykon and scattering his forces, SpoonyBard Elan activates a self-destruct rune that blows up the entire dungeon, because he wanted his dramatic OutrunTheFireball scene. Turns out that the self-destruct took out the magical Gate that was [[spoiler:sealing away a world-destroying abomination, so the loss of the Gate brings the world one step closer to destruction]]. The only consolation of this massive act of stupidity was the Gate couldn't be recaptured by the BigBad later on (and the Order wouldn't have known that he might try). They ultimately decide that in hindsight, this was the necessary thing to do, even if they didn't know it at the time.
** Later on, [[KnightTemplar Miko Miyazaki]] [[spoiler:destroys the Azure City Gate]] unnecessarily. Worse yet, she chooses precisely the wrong moment to do so. If she had been stalled for even a few more rounds, [[spoiler:[[BigBad Xykon]] ''and'' [[TheDragon Redcloak]] would be dead]], which among other things would have denied the goblin army its powerful and competent leadership.
** Later yet, [[BunnyEarsLawyer Celia]] manages to [[spoiler:reach a settlement with]] the local Thieves' Guild. While this fixes a lot of immediate problems, one outcome was that [[LovableRogue Haley]] [[spoiler:(who deserted the Guild in the past) must give 50% of her loot to the Guild to maintain the fiction that she never really left.]] Since she needed all of it for her [[spoiler:"get her father out of jail"]] plan, she is... upset, to say the least.
*** [[FromBadToWorse To make things worse]], Haley doesn't even have most of [[spoiler:her past few years' worth of loot]] any more, having lost [[spoiler:most of a dragon's hoard [[http://www.giantitp.com/comics/oots0245.html in a fire]]]]. Just to break even, she'd have to [[spoiler:steal twice that much all over again and give it all to the Guild -- half belonging to the Guild outright, and the rest paying off her debt to them]]. Haley's solution? [[spoiler:Desert the guild all over again, killing [[EvilCounterpart Crystal]] while she's at it,]] when the Order gets together again.
** Girard, one of the [[spoiler:creators of the Gates]], was paranoid that his former associate [[spoiler:and fellow Gate-maker Soon]] would break their vow and try to interfere with [[spoiler:the Gates]]. So he gave [[spoiler:Soon, and nearly everyone else,]] the wrong coordinates, booby-trapped the decoy area, and gave the real location to the one person he trusted, [[spoiler:Serini]]. Thing is, his associate never broke his word, being a [[HonorBeforeReason paladin]]. When the decoy area is approached years later by the Order of the Stick to try and defend it from [[BigBad Xykon]], they're almost killed by Girard's paranoia and have no idea where the real location is. And guess who has his bony hands on [[spoiler:Serini's diary]]?
** In ''Start of Darkness''...
-->'''Lirian:''' Even if you locate them, my friends will stop you from [[spoiler:conquering the other four Gates.]]
-->''(BeatPanel)''
-->''(BeatPanel)''
-->'''Xykon:''' Did you- Did you just say, [[spoiler:"the ''other'' four Gates"?]]
-->''([[RuleOfThree Beat Panel]])''
-->'''Lirian:''' Crap.
** Vaarsuvius, while drunk on [[spoiler:the power of three epic evil spellcasters]], defeats a black dragon that was menacing [[AmbiguousGender his/her]] family. He/she casts [[spoiler:the genocidal spell ''Familicide'' on the dragon, exterminating the dragon's entire bloodline]]. Later it's revealed that [[spoiler:Girard Draketooth, the epic-level illusionist that is charged with protecting one of the all-important Gates,]] was the grandson of a relative of said dragon. Thus he and his family [[spoiler:were wiped out by the spell, leaving the Gate defenseless]]. He/she then went on to attack Xykon, resulting in [[spoiler:Xykon and Redcloak finally getting motivated to move out and attempt to capture another Gate, since they'd [[OrcusOnHisThrone gotten complacent]] after conquering Azure City]].
* In the first chapter of ''Webcomic/GunnerkriggCourt'', Antimony helps a lost [[LivingShadow Shadow-Man]] return to his [[TheLostWoods forest home]], by assembling a Robot to escort him there (since the rules prohibited Annie from going herself). She also tells Robot that he only has to return to the Court afterwards if he wants to, so he decides to go exploring the woods. Several chapters later, Robot returns, [[DemonicPossession possessed]] by another, violent and malicious shadow-creature, and the process of stopping the shadow results in Robot getting impaled on a {{BFS}} and deactivated. A few chapters later, Annie finds out that the people of the forest have not been on good terms with the Court for the past decade, and that they [[MagicVersusScience hate technology on principle]]. Nice job completely screwing over your friend ''and'' causing a diplomatic crisis, hero.
* ''Webcomic/EightBitTheater'' has a nice scene where Muffin [[spoiler:Dragoon's pet parrot (dragon)]] reveals to the light warriors that Bahamut, [[spoiler:who they had previously awakened, would only awaken when the world is about to be destroyed.]] Only Red Mage seems to care, though in retrospect any acts of "good" the Light Warriors do usually makes everything worse for someone else.
* During the "Sin City" (no, [[SinCity not that one]]) [[StoryArc arc]] of ''DominicDeegan'', Dominic reveals to The Infernomancer that the demon lord he was supposedly bound to serve didn't have control over him, meaning he didn't have to follow any orders. The Infernomancer's response? "Now I get to kill you the way I've always wanted to -- ''slowly!''"
** Not to mention the "War In Hell" arc, where Dominic helps out Karnak the whole time only to realize he probably shouldn't have been helping Karnak this whole time.
*** In his defense, Karnak's death would have also killed Szark Sturtz, since he and Karnak will linked by a wound Karnak had inflicted on Szark when the latter was a child. You really can't blame Dominic for trying to keep his best friend alive. Plus, as pointed out by Dejah, there was really no way for the war to end positively for humanity.
** And then there's Klo Tark, who started a prison break to (rather circuitously) save Dominic's life.
* In ''{{Starslip}}'', the crew (mainly Quine, though Vanderbeam initiated it) have done a Nice Job Ruining The Quel's Utopia.
** And again with the Anthelerix. Both cases were such colossal screwups that Vanderbeam has since repeatedly suggested that Quine would do a better job of doing his job if he were to just sit quietly on the Paradigm someplace where no one has to look at him.
*** That comment is more due to Vanderbeam's irrational hatred of Quine. In the Anthelerix's case, the responsibility arguably rests with Admiral Huff. You'd think that the ''Paradigm'' being teleported back to Earth was a sign that maybe the Anthelerix didn't want anyone disturbing them for the time being, but noooo...
* The party of ''Webcomic/DarthsAndDroids'' pretty much does this all the time.
** One of the more obvious examples was completely ruining Darth Maul's attempt to retrieve the [[MacGuffin Lost Orb]] (and also setting up [[spoiler:Jango Fett's revenge]]).
** However, the prize for most unintentional consequences goes to Jim for his attempt to rig the pod race. Let's see...
*** He sold weapons to the Sand People and made them a promise he didn't keep; they went from peaceful and meditative to vengeful and armed.
*** His later embellishments to the plan actively worked against his earlier, almost-reasonable schemes.
*** And if the course of the strip is close enough to the movies, then he also inadvertently created Darth Vader and ensured the destruction of the Jedi. All to win a bet.
*** In Jim's defense, they ''did'' win. But it should be noted that they only got into that pod race to raise money for weapons ''they never used anyway''.
** One of the players accidentally mistakenly referred to a [[http://starwars.wikia.com/wiki/Nexu nexu]] as "Nixon", thereby giving the DM ''ideas''. Now, [[TheVietnamWar what]] [[RichardNixon contemporary]] [[{{Scandalgate}} 70's events]] gave GeorgeLucas the inspiration for TheEmpire's formation, again?
* The ''FreakAngels'' had wanted to [[spoiler: cause a huge but non-threatening destructive gesture as a means of putting the army off the notion of continuing to chase them (or at least distracting them for a while]]. Instead, their ''severe'' underestimation of just how powerful they are [[spoiler: caused them to inadvertantly cause destructive shockwaves which ended civilisation]].
* Thomil of ''{{Juathuur}}'' accidentally kills [[http://oneway.juathuur.com/1/?strip_id=65 Beshren's daughter]]. Ratheel is even worse when it come to [[http://oneway.juathuur.com/1/?strip_id=326 breaking useful stuff]].
* [[http://www.brawlinthefamily.com/?p=1166 Part 5]] of the "Snake in the Grass" storyline in ''Webcomic/BrawlInTheFamily''. [[spoiler: At least the date ended well...]]
* ''Webcomic/WarbotInAccounting'' is already GallowsHumor enough, but [[http://www.nuklearpower.com/2010/06/07/warbot_14-the-all-nighter/ look what happens]] when Warbot actually tries to ''help''...
* In ''Webcomic/{{Homestuck}}'' Jade sends her friend John a birthday present. [[spoiler: Using her precognitive abilities, she sends John a weapon to fight [[DiscOneFinalBoss Jack Noir.]] Unfortunately, the Noir intercepts the gift and ends up using it to defeat the black queen and take her power. Jack then uses this power to singlehandedly obliterate both the black AND white armies and destroy the entire planet of Prospit, which ends up also killing Jade's dream self. Nice job.]]
** In Act 5, we finally find out why the {{Troll}}s think the kids fucked up the game so badly. [[spoiler: It's actually ''their own fault'', as Vriska made John fall asleep, forcing [[RealityWarper Bec]] to prototype Jade's kernelsprite with himself, and granting [[DiscOneFinalBoss Jack Noir]] near-omnipotence.]]
** Then there's Karkat's big screw-up, which more or less caused everything that ever went wrong. [[spoiler: He was in such a hurry to beat the game that he decided that the final frog needed to fix Bilious Slick's genetic sequence was unnecessary. Turns out that code was the only thing preventing the frog from getting a massive tumor, meaning he essentially gave the kids' universe cancer.]]
** Played with during The Green sun incident [[spoiler: While Rose and Dave and the rest were trying to destroy it, they end up creating it with their actions. Aside from all the complexities of predestination and causality, the Green Sun isn't a bad thing, it's a neutral power. While it powers Doc Scratch and aids in the creation of [[BiggerBad Lord English]], it also powers Bec, and he's the one who saves Jade and makes sure she get's in the game.]]
* In [[http://www.smbc-comics.com/?db=comics&id=528#comic this]] ''SaturdayMorningBreakfastCereal'' strip.
* A recent ''ExterminatusNow'' comic had Yuri smash a panel that she thought was the power source for the daemon portal. Turns out, it may have been the control panel, given that its destruction released the daemons.
* In ''PennyAndAggie,'' when Stan confronts the [[TheSociopath sociopathic]] Cyndi about her attempt to deceive his best friend Jack, and other classmates, into thinking she wanted to sleep with them, he taunts her for not thinking big enough, so as to imply she's lost her touch and shake her confidence. Instead, she says "You're right. You're so right," and [[EvilLaugh giggles ominously]]. Stan himself admits in the next strip that he made things worse.
* The bad guy of PlanescapeSurvivalGuide took a few minutes to explain in detail to Milny exactly how she broke everything in [[http://planescapecomic.com/177.html this episode]].
* In ''Webcomic/CuantaVida'', Bleu fails to kill the RED Sniper, as he (Bleu) DoesNotLikeKilling. This leads to [[spoiler: RED Spy's death when he [[TakingTheBullet takes a bullet]] for BLU Sniper]], which in turn leads to [[spoiler: the introduction of Rojo, who loves nothing more than [[FateWorseThanDeath mutilating]] his opponents]]. [[SarcasmMode Nice going, Jordi!]]
* Congrats, [[{{Goblins}} Big Ears]]! [[spoiler:Your CriticalFailure at healing Complains' fractured arm has lead directly to Chief dying a slow, agonizing death.]]
* In ''Webcomic/ElGoonishShive'', Abraham and his great idea to make the Dewitchery Diamond. What he needed was to remove or suppress the lycanthropy of ''one guy''. What he did is create a BoobyTrap for [[http://egscomics.com/?date=2006-05-05 unaware shapeshifters and users of cosmetic magic]], with [[NecessaryDrawback side effects]] that in turn suffer several other side effects in such a way that whatever problem caused its activation ''spreads''. And it's nigh indestructible, so all this fun never ends.
** [[LordOftheRings They need to find a volcano and a hobbit or two.]]
*** It was [[DidntThinkThisThrough Abraham]]. Others mostly settle on locking damn thing away.
** Lets not forget the fact that good ole' Abe thinks it might be ''intelligent!''
** Raven points out that he could have just used the diamond to ''buy a healing spell from a better mage''.
* In ''Webcomic/TalesOfTheQuestor'' Quentyn is sent on a quest to slay a dragon. He actually succeeds, but only after that success does he learn two critical facts:
## There were [[spoiler: ''two'' dragons, not one]].
## The one true BerserkButton for dragons is [[spoiler: finding the body of a dead dragon]].
** The direct consequence of this is that [[spoiler: the second dragon runs amok and lays waste to the Duchy Quentyn was trying to save]]. There are also hints that more long-term consequences await Quentyn in the form of [[spoiler: a CorruptChurch whose attention was grabbed by this incident]].
* During the 1999 arc of ''{{Asperchu}},'' Jivin stops past Bionic from committing suicide over Ian's rejecting of him. Considering the things Bionic would do in the present, it might have been better for everyone to let him die.
* In ''Webcomic/GirlGenius'', [[http://www.girlgeniusonline.com/comic.php?date=20121126 Agatha blasting a free path toward the astronomy tower...]] [[spoiler:and blasting the tower at the same time.]] Can we just say, "Whoops"?
** Much earlier, a totally-ignorant-of-her-true-bloodlines Agatha Clay [[http://www.girlgeniusonline.com/comic.php?date=20040310 blows her stack when groped by a minor researcher]] on [[CoolAirship Castle Wulfenbach]] and tells the man to go do whatever it was he should be doing. Bad News: the guy is a [[ManchurianAgent thoroughly conditioned sleeper agent]] of the mysterious long-missing entity called [[BigBad The Other]], [[spoiler: who happens to be the mother of the teenaged girl that was screaming in his face]]. Worse News: a creation of The Other known as a Hive Engine was recently brought aboard, and activating it to unleash the monsters within is exactly what The Other's servants should be doing.
* Cale, the protagonist of {{Looking for Group}}, has a long history of causing this kind of events. Due to his status of {{Wide Eyed Idealist}}, who has the misfortune of living in a {{Crapsack World}} [[BreaktheCutie which loves to prove him wrong]]. In chronological order:
** The omnipresent example would be his friendship with [[TokenEvilTeammate Richard]] [[EnsembleDarkhorse the Warlock]], whose {{Stupid Evil}} tendencies tend to cause more damage to those they try to help than they prevent. It never occurs to him than the people of the world may be better off without them trying to help, [[http://www.lfgcomic.com/page/708/ until it does]]. [[IgnoredEpiphany Too bad it doesn't lasts.]]
** Unifying the northern races to fight against [[TheEmpire Legara]], but his search for more allies, led to [[YouAreTooLate them being too late]] to join the major battle against their common enemy which led to the death of a supporting character and the capture of another.
** Killing [[spoiler: Tavor]], who was the leader of [[TheEmpire Legara]] and caused the much more competent [[spoiler:[[WellIntentionedExtremist Aellon]]]] [[DragonAscendant to take over command]].
** [[http://www.lfgcomic.com/page/687/ Sometimes these actions are played for laughs]].
-->Looked like he needed a win.
** And now [[spoiler: killing Aellon]], ruining the chance of the people of Kethenecia to achieve a lasting peace with Legara, action which finally causes [[spoiler: Benny to leave him and the party to split]] and forcing them to retake the adventure after a {{Time Skip}}.
* In ''Webcomic/{{Narbonic}}'', Artie the super-intelligent gerbil decides to literally make friends by dosing several other gerbils with intelligence serum. One of the gerbils escapes and creates a group of Objectivist hamsters. Later on, Artie meets the hamsters and gives them a million dollars which they use for their plan for WorldDomination. Even later, Artie breaks up Helen and Dave's relationship as he believes that Helen is taking advantage of Dave. The break-up precipitates Dave's StartOfDarkness. During the efforts to simultaneously thwart the hamsters and Dave, Artie brings up his status as TokenGoodTeammate, and Helen [[WhatTheHellHero calls him out on it.]]
* Webcomic/{{Spacetrawler}} features a group of protagonists on a quest to liberate the Eebs, a SlaveRace of super-intelligent aliens who've been "brain-clamped" into having no will so they can be exploited for technology. They successfully rescue some, only to discover that un-clamped Eebs are actually a race of natural sociopaths with incredibly powerful telekinesis. And a dozen of them working together can firestorm an entire planet from orbit in seconds. Oh, and they're also kind of pissed about being enslaved. The rescue mission ends up with a body count in the ''billions''.
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