The crew defeat the fallen power Jasmine, who took over the world through mind control and was eating people on a daily basis... and are later rewarded by the demonic law firm Wolfram and Hart for "Ending world peace" because during the short time Jasmine was in control, there was no war or fighting or hatred anywhere within her influence.
However, the Senior Partners actually intended to corrupt Angel and distract him from their planned apocalypse all along.
Also an example: waking Jasmine up in the first place by curing Cordelia's amnesia.
After Angel and his team assassinate all members of the Circle of Black Thorns, the evil forces of the world decide to pull out all the stops and unleash every available evil creature on LA.
What's worse is the demonic army is just the beginning. Wolfram and Hart's real reaction to Angel taking out the Circle is to send the whole of L.A. - every man, woman and child - to Hell.
Also used in the episode "The Ring":
Wesley: We set the captives free.
Cordy: Well, actually, didn't we set a bunch of demons free?
Wesley: Oh. Well. Technically, yes.
Fortunately not all demons are evil, but we can't vouch for everyone they set free from the gladiator ring.
The Aquabats! Super Show!: At the start of "Cowboy Android!", a miner tells the Aquabats off for sealing a monster in the mine rather than getting rid of it, as this means they still can't work in the mine.
Atomic Train: In this TV movie, a train driver following behind a runaway train in an attempt to rescue the occupants, ignores orders to pull back, muting his radio in the process. With the radio muted, he is unable to hear the fact that the runaway has managed to stop. This results in him ramming into the rear of it, causing it to run away again.
Nice job taking the tougher, advanced battlestar capable of building Vipers and ramming it into a Cylon Basestar to save the aged, more obsolete battlestar, Lee. Especially since the Galactica is now falling to bits entirely.
Nice job creating an army's worth of Cavils and their war machine and letting them box you, Saul, Ellen, Sam, Galen, and Tory.
Nice job killing Tory on the spot and losing any chance of peace with the enemy Cylons, Galen.
How about what lead to the fall of the Twelve Colonies and the near-extinction of the human race? Nice job thinking with your dick and giving the mysterious woman you barely know, access to the Colonial defence systems in exchange for sex, Baltar!
FBI Agent Seely Booth allowed a man convicted of killing a teenage girl (and was less than 30 hours away from being executed for the crime) convince him to reinvestigate the case by providing crocodile tears in prison. He did eventually learn that he was right about the man being the killer all along, but said investigation turned up even more bodies, which prevented the man from being executed before the investigations could be completed (which would likely take years). Even worse, the killer eventually escaped from prison and killed another woman and ended up stalking his potential love interest, Dr. Temperance Brennan. Seriously, nice job breaking it, hero.
In another episode, Booth comforted a woman who had been stalking that week's victim, causing her to become obsessed with him. This led to the woman trying to kill Bones out of jealousy, Booth getting shot while protecting Bones, and Bones shooting and killing the woman when she tried to shoot her again.
When Faith begins to go bad after staking the Deputy Mayor, Buffy and Giles plan to deal with it without alerting the Watcher's Council, but Wesley finds out anyway after eavesdropping on them and immediately calls in a special ops team to bring her in. In the process of doing so, he completely ruins Angel's attempts to get through to her just as he was beginning to succeed, setting off a sequence of events that lead to Faith becoming Mayor Wilkins' dragon.
Happens in the season four episode "Fear Itself":
Giles:(flipping pages) I have it, I have it. Uhm, "The summoning spell for Gachnar can be shut down in one of two ways. Destroying the mark of Gachnar..."
(Buffy walks over to the mark and puts her fist through it, ripping up the floorboards. Gets up and looks over at Giles with a proud smile)
Good thing the fear demon itself is only four inches tall.
Buffy does Angel, which causes him to lose his soul and revert to his evil mind rapist self. Nice job having the hots for a vampire, slayer. Of course, Angel gets equal blame for not keeping it in his pants despite knowing full well his curse.
Played straight - somewhat - with the demon Balthazar in Season Three. Balthazar was Mayor Wilkins' rival - had he regained his power, he would have killed the Mayor. By killing Balthazar, Buffy eliminated one of the two major threats to the Mayor. Of course, the other major threat was herself...
And, of course, when Buffy was brought back from the dead, thereby ripping her out of heaven. From Buffy's point of view, at least, nice job breaking me, Scoobies.
Then in Season Eight Buffy needed funds, stole from a bank... which resulted in a rogue Slayer and a very unhappy military. Giles sent Faith undercover to assassinate a dangerous Slayer. Buffy misunderstood. Faith didn't react well. Willow's flaying of Warren comes back to haunt her. And everyone else. That was just the beginning.Nice job- oh never mind.
Buffy created the Twilight dimension by screwing Angel, which let thousands of demons invade Earth, which resulted in the destruction of the Seed of Wonder and removed all magic from the world.
While we're at it, nice work imitating Twilight, becoming possessed and killing Giles, Angel.
Buffy destroying the seed in Season 8. Willow blames Angel.
Nice job turning your back on Management in one finale and shooting Strickler in another, Michael. You now have even less of a clue about what's going on, and you almost got yourself into even hotter water.
This seems to be a running theme for each season cliffhanger, but most notably when Michael finally seemed to have beaten those responsible for his burn notice, only to find out that his efforts unearthed the man in charge of the entire conspiracy that resulted in Michael's burn notice and who forced Michael to work for him under the threat of having Fiona locked away.
Charmed: The episode "Coyote Piper" revolves around a spirit escaping from her demonic scientist creator. She eventually possesses Piper, and uses Piper's body to get her sisters to kill the demonic scientist when he comes to look for his creation...making it significantly harder to deal with the spirit. The demon's final words "You fools! She will destroy you!", are somewhat apt.
Combat!: In about 8:23 of this clip from this 60s-era World War II series. One of the characters says "Nice going, hero" after another is forced to shoot a German sentry they were supposed to take alive, not only depriving the unit of a prisoner to interrogate but also attracting the unwanted attention of even more enemy troops.
In the episode "The Long Game", the Doctor thinks he's saving the world by shutting down a space station that controls an Earth-spanning propaganda regime. In the season finale, however, he returns to Satellite 5, a century later - and learns that as a result of the shutdown, Earth has become technologically and socially stagnant, and the station itself has become a clearinghouse for reality shows, secretly run by the Daleks.
It's also been suggested (including in a column by Russell Davies) that the Doctor's self-righteous overthrowing of Prime Minister Harriet Jones after her actions in "The Christmas Invasion" directly allowed the Master to take her place, conquer the world, and rule in an unequalled reign of terror and genocide for an entire year until things managed to get sorted out. By contrast Harriet's truncated term, according to the Doctor himself, would have been "a Golden Age". Nice going, Doc.
Originally, this was going to pointed out by the Master in "The Sound of Drums"/"Last of the Time Lords". However, it was decided that this sort of gloating — in addition to the abuse the Master had already heaped upon the Doctor — would be an overkill.
It also allowed the Prime Minister seen in Torchwood: Children of Earth to come to power. Perhaps Harriet Jones would have had stricter morals about dealing with the 456.
Which also means the Doctor is responsible for causing even more pain and suffering to a friend, since it's the lack of government action that leads Ianto to die with Jack confronting the 456, and Jack to sacrifice Steven.
And to go more Old School (or DVD-school): Did you know it was the Doctor who gave Nero the idea to burn Rome?
At the end of "The Waters of Mars", it's heavily implied that the Doctor broke Time itself. Or, rather, he would have if Adelaide had not made the ultimate sacrifice to set things straight.
And let us not forget that in "Tooth And Claw", the Tenth Doctor and Rose save Queen Victoria from a werewolf, but because they act like selfish, immature adrenaline junkies, she decides to found the Torchwood Institute to protect the British Empire against extraterrestrial threats. They then spend a good century robbing and murdering innocent alien passers-by, and nearly destroying the human race several times For Science!.
And in "Victory of the Daleks" the Doctor's attempt to force the Daleks to admit their true intentions culminates in him screaming "I AM THE DOCTOR, AND YOU ARE THE DALEKS!". Unfortunately, this "testimony" causes the Daleks' Progenitor device to accept that they are the Daleks (apparently it didn't recognise them as they weren't 'pure'). At this point they reveal their true identity, start killing people and make more Daleks which proceed to turn on all the lights in London during the Blitz, make an earnest attempt at blowing up the Earth and then escape to their own time period to recover and rebuild. Nice job endangering the entire universe throughout the whole of history, Doctor.
This trope comes up a lot with the Daleks. The Fourth Doctor had a chance to destroy the Daleks back at their creation, at the request of the Time Lords ("Genesis of the Daleks"). All he had to do was touch two wires together. Not only does he refuse, he keeps his companion Harry from doing it. Reason? What about all the good that might have been accomplished because the Daleks exist? Dare he destroy an entire race, even an evil one? Of course, years later he does just that, only now, because he waited, he's annihilating two species, the Daleks and his own. And that to stop a war that he himself could have prevented.
One Eleventh Doctor comic suggests that not only was the Fourth Doctor's refusal to kill the Daleks the cause of the eventual genocide he created, but actually "the first shot" in the Time War, which caused the Daleks to retaliate against the Time Lords and lead them into the war that resulted in their double genocide by the Doctor in the first place.
Bonus points for the Time War. The Doctor "ended it" by killing off the Daleks and the Time Lords, right? Wrong! Some Daleks have escaped and are regular villains in the new series. The Doctor has been good at keeping the Time Lords dead, though. Nice job, Doctor.
Eleven runs into this again during "A Christmas Carol". He resorts to going back in time and rewriting the entire childhood of Kazran, the only man who can save a spaceship from crashing, only for Kazran to end up exactly as bitter and jaded as he was already, just for different reasons. Then, when Kazran finally does agree to help, the all-important machine no longer recognises him as the man it's programmed to obey.
Of course, the Doctor's rewrite involved an act of kindness that kind of backfired: he let Abigail out of her cryogenic prison every Christmas, not realizing that every day she left was one day closer to her death- up until she had one day of life left. When Kazran realized this, it brought about the bitterness mentioned above.
The Doctor has a lot of these concerning the Daleks. First he visited their home planet of Skaro, alerting them to the existence of life off of their little rock, thus causing them to become intergalactic genocidal monsters. Then much later on he causes the biggest backfire in history which involves a Dalek Death Ray destroying Skaro. This of course was probably a large reason for the Time War, and we all know how that ended.
In the 2005 episode "Father's Day". Rose saves her father from the car that's supposed to kill him despite the Doctor warning her not to do more than SEE him physically. Cue the Reapers appearing and starting to devour everyone in sight just to heal the wound she's created. It gets worse, though. When the Doctor finds a solution that will bring everyone back and keep her father alive, he warns her not to touch her past self. Rose, of course, does this (well, her past self was thrust into her arms), ruining the Doctor's solution and getting him consumed in the process. As a result, the only way to stabilise time is for Pete Tyler to sacrifice himself ... Rare case of the hero breaking it twice in one episode.
In The Movie, the Doctor is rushed to hospital after being shot, where the cardiologist on duty, Grace, begins to operate on him, despite the Doctor repeatedly trying to get her to stop due to his Bizarre Alien Biology (finally being silenced by being pumped full of anesthetics). During the operation Grace gets lost and freaks out due to the Doctor's different biology, a medical probe breaks off inside the Doctor, and he has a seizure and dies. It gets worse however, as when his regeneration finally kicks in it's botched up due to the ton of anasthetics, and the Doctor ends up wandering around the hospital confused and with amnesia. All this could have been avoided if Grace simply hadn't operated on the Doctor.
Yeah, try telling a doctor not to operate because you are an alien. And you look completely human. And the doctor has never before encountered aliens.
In "Utopia", Martha Jones convinces Professor Yana to open his Chameleon Arch pocket watch, which turns him back into the Master.
In the Fall 2011 season trailer, Hitler thanks the Doctor for saving his life. (Technically, this was Mels'/ River Song's/Melody Pond's fault since she threatened the Doctor at gun-point, shot the TARDIS and caused it to crash at the wrong time. Doesn't stop the Doctor from saying this:
The Doctor: It was an accident, believe me.
Fans waffle back and forth about what was happening in "Partners in Crime." Miss Foster was farming fat to create the Adipose, and some fans believe that she always intended to kill the humans eventually. However, others notice that she says that they only kill humans "in a crisis" (by converting non-fat tissue, like bone and organs, into fat) and that it makes them sick (something she, as a nanny, would try to avoid.) It was only after the Doctor and Donna start to interfere that she stops farming fat and starts farming whole people. Even the Doctor said as a diet plan, it wasn't that bad; quick, painless, and efficient (about one kilo of Adipose walked away every night.)
This is pretty much answered in "Turn Left" when we see what would have happened had the Doctor and Donna not been there. It was not pretty. (Can somebody say 'mass genocide'?)
In "Family of Blood", the Doctor masquerades as a human in 1913 rural England to evade four aliens who want to steal his longevity. Assuming they don't find him, they die of old age in a few months, right? Wrong! Of course, they do find him, and go on a rampage, killing many innocents. In the end, the Doctor re-emerges and saves the day. Victory, right? Wrong! Love interest Joan, grief-stricken at the "death" of the Doctor's manufactured human self, points out that all the death and suffering was the result of the Doctor coming in the first place. By trying to be kind to the bad guys, he ended up being cruel to the innocent bystanders. Even the Doctor seems to accept that this is true.
In the season 6 episode "The Girl Who Waited" the Doctor managed to create an alternate Amy who has lived in solitary confinement for 36 years, is bitter with loneliness and hates the Doctor, and forces Rory to make a Sadistic Choice. He could have avoided it if he'd remembered there was a plague on the planet they'd landed on.
In an attempt to save the Doctor's life, River Song tries to overcome her programming to shoot the Doctor by wasting all her shots, breaking what should be a fixed point in time. As such, all of causality breaks down, and all of existence on Earth happens at once. The Doctor berates her for her willingness to hurt all of reality for him, but in an odd turn for a hero, she doesn't care. In the end, it turns out the Doctor had his own plan for getting out of it, so she really need not have bothered.
In the 2005 episode The Long Game the Doctor thought that he had helped the human race when he shut down Satellite 5, a manipulative organization that turned the Earth into a dictatorship. However, when he returns 100 years later in the episode Bad Wolf he is told that after he interfered the government and economy on earth fell apart, leaving it a mess. It didn't help that he'd only taken out the middle-men...
Of course, the most disastrous Who-related example was not committed by the Doctor at all, but by the BBC. Way to erase most of the early episodes, guys.
Not just Doctor Who — a great majority of BBC series of the '50s, '60s and '70s were his with this policy. It was so bad that Dudley Moore and Peter Cook begged and pleaded with the BBC to give them the master copies of their series Not Only But Also that were scheduled for wiping, and even offered to buy new videotape to replace the masters to be wiped.The BBC refused.
Eternal Law: In one episode, the angels' case of the week is preventing a woman from committing suicide. By the end of the episode she seems to have found some sort of peace, despite going to jail for murdering her son's killer... and then Tom reveals himself as an angel and promises she'll be reunited with her son in heaven. She promptly commits suicide to get to the afterlife straight away.
In virtually every episode, when Urkel comes in contact with something, usually one of Carl's prized possessions, usually followed by Urkel uttering one of his catchphrases, "Did I do that?"
In one case, "nice job breaking it" set up an entire plot where Urkel was unusually angry at Carl and declined to explain; he kept swatting Carl on the head with a newspaper. It turned out an Urkel in shining armor had broken Carl's prized model ship-in-a-bottle that had been left prone on the kitchen table, thanks to the nerd's awkward handling of a lance. Carl — unwilling to see the whole thing was his own fault due to leaving the model ship where it could get broken — was very angry and threw the nerd out of the house, before fuming aloud that he'd wish Urkel would just go away forever (Urkel had accidentally overheard Carl rant about his broken ship). Carl eventually realizes his words were inappropriate and apologizes.
This however can be considered a Broken Aesop due to the number of times Steve as pulled the Wounded Gazelle Gambit. Laura eventually called him out on the fact that every time she gets fed up with his antics he guilt trips her into forgiving him.
Farscape: Nurse Kelsa from the episode Different Destinations. Without assessing the current situation using either her own eyes or trying to seek and explanation from Crichton, she decides to put an arrow though the chest of an imprisoned enemy General that was about one hour away from brokering a peace deal that would have protected the women and children from slaughter. The results? she is not only technically responsible for the deaths of everyone present (including the one man that survived in the original timeline) but was also responsible for nearly destroying the future of that entire part of space. The best bit however comes later in the episode when she still refuses to believe Crichton was innocent of treason and threatens to shoot Aeryn when she tries to untie him even though she was standing right there when another enemy official confirmed everything Crichton had claimed and basically pointed out that she was responsible for dooming them all. To give her credit though; she is saved from Too Dumb to Live status by the fact it was the main cast travelling back in time that put her in that situation in the first place - breaking it long before it was her turn to.
FlashForward: During the Mosaic team's trip to Somalia, their resident morally-ambiguous CIA agent Vogel kills the one man who was destined to bring peace to the war-torn nation. He doesn't seem to care too much.
The episode "The Preachification of Convincing John": Mokey decides that eating the constructions Doozers work so hard to build hurts their feelings. Without bothering to ask the Doozers themselves how they feel about the situation, she enlists the help of Convincing John to convince all of Fraggle Rock that eating Doozer constructions is wrong and binds them in the nigh-unbreakable Solemn Fraggle Oath never to do so again. So the Doozers build and build with no one to eat the constructions — and end up crowding both themselves and the Fraggles nearly out of house and home. Eventually, Mokey overhears Doozers lamenting about having to move out of Fraggle Rock. She realizes she had them all wrong. They like the Fraggles crashing in since it means they can keep on building, and she quickly undoes the Oath.
Nice job crossing to the other universe and saving the other Peter from dying, Walter. Now the fabric of reality is tearing itself apart.
And Olivia, nice job alerting Walternate about the existence of the Primary Universe the first time you crossed over. Now he knows where his son is and wants revenge.
Ghost Watch: The parapsychologist Dr Pascoe in this infamous BBC special wants to use the program to justify the family living in the haunted house and bring their suffering to public attention. By doing this, she ends up creating a massive, nationwide sťance that amplifies the ghost's power across the entire country.
In the season 2 premiere episode, Rachel's Attention Whore tendencies cause a new girl who is an awesome singer to join Vocal Adrenaline after she sends her to a crack house to keep her from stealing her spotlight. Though the only reason that the girl joined Vocal Adrenaline was because Sue made a call to the new VA coach because Will wouldn't help her antagonize the new football coach anymore.
Admittedly, almost all of the glee club's problems are caused by the stupidity/selfishness of Will or one of the glee kids (usually Rachel or Finn). This happens pretty much Once per Episode just so everyone can learn An Aesop at the end.
On Growing Pains, Michael discovers that the school is going to fire Coach Lubbock due to budget cuts. After failing at every legal move to prevent this, Mike organizes a sit-in. This results in the protesters all getting arrested and the school fires Coach Lubbock immediately due to the negative attention. Michael ended up accelerating the very thing he was trying to prevent.
Had two in a single episode now (though one got started a few episodes prior): Arthur Petrelli is able to get off life support by stealing Adam's healing power — which he had easy access to because Angela sent Hiro and Ando off to release Adam in a bid to stop Arthur's schemes. Later on, Peter storms Pinehearst on his own, finds Arthur there, and subsequently gets his powers stolen.
According to Angela Petrelli, Future Peter was responsible for Sylar acquiring Claire's healing power. As Angela put it, "She had a very bad day."
The season 1 episode where Isaac tries to shoot Peter, in an attempt to prevent him from becoming the human nuclear bomb seen in the future paintings. When Peter becomes invisible, Isaac shoots at a noise behind him...and accidentally kills Simone, who wanted to help Peter.
When Sylar tries to kill Elle, she renders him unconscious with a massive blast of electricity. Unfortunately, she also overloads the Level Five power grid, allowing all of the super-powered prisoners to escape.
Nathan Petrelli initiates a government program to round up persons with superhuman abilities in order to protect regular citizens. But he is forced to flee when he is revealed to have an ability. As a result, Emil Danko takes over the operation; unlike Nathan, he wants to kill all so-called evolved humans, viewing them as nothing but animals. Not only does Danko murder Daphne Millbrook and (almost) Traci Strauss (although she returns in the next season and was also hinted to have survived in the episode itself), he then enlists Sylar to help him carry out his nefarious plans!
Then there's the Charlie issue. Hiro decides he can't save her life as she's already dying, so forgets about her, as do the writers. But at the very least he could have saved her from being killed by Sylar instead of allowing Sylar to take her ability.
He fixed it in the fourth season though.
How did Samuel Sullivan find out about the nature and true extent of his powers? Because Mohinder opened a box with research that his father expressly wanted never to surface and traveled all the way to his carnival of horrors to blab about it, of course. It's almost as if the writers hate his character too and wanted to give even newcomers a reason to hate his ass.
They also once cured a patient only to find out that he was a serial killer. Had their research skills been up to snuff, they could have taken certain obvious measures.
House taking a mental patient out to give him his life-long dream of being able to fly leads to the guy actually believing he can and jumping off a building.
House of Anubis: Eddie and KT using the Staff of Osiris- which unleashes Ammut, the same goddess they were trying to prevent from being unleashed. It's kind of fair because the villains have tricked them into thinking the staff would stop Ammut, however, they did nearly help said villains destroy the world.
JAG: In the season four episode "Innocence", Harm first thinks that heís made a deal with the Japanese prosecutor who smiled and bowed in a friendly manner. It turned out that he had been greatly offended and had contacted the Japanese Prime Minister who told the press that U.S. Authorities were uncooperative and obstructive, and thus forced them to handover the suspect to Japanese authorities.
Jericho: Jennings & Rall and Ravenwood are getting their hooks into the US government, even going so far as to suborn a plan to safeguard Russian nukes. John Smith decides the best way to fix things is to set the bombs off in cities containing J&R's branch offices and central HQ.
Kamen Rider Decade: If we are to make sense of Wataru Kurenai's contradictory babblings, mentioned that the eponymous Rider has to kill all the Riders to prevent the merging of the Alternative Rider Worlds, mentioning that "creation cannot begin without destruction". Instead, Decade chose to help all the Riders defeat their respective monster enemies as a Rider should. Cue Dai Shocker (the coalition of all the enemy organizations and monster races) through Apollo Geist becoming able to speed up the destruction of the Alternative Rider Worlds. Thankfully, Decade eventually turned into his nasty, somewhat evil Fury Form after being given a major beatdown by the original 9 Riders for all his troubles, thus being able to kill all Riders, trap them into cards and allowing the worlds - fallen riders included - to be rebooted to their proper states, but what the hell, Heroes?! What did they really have to do?! There was a lot of Mind Screw going on, but it seems attacking Decade was simply to goad him into becoming Decade Fury so that he would do what needed to be done.
Kamen Rider Fourze: In The Movie, the heroes get recruited by a secret government organization to stop the evil Space Ironmen Kyodain from attacking Earth with a Kill Sat, and are chased the entire way by a Dark Action Girl. On the Kill Sat, they use explosives to destroy a number of power stations...but only too late do they find out that their benefactors are the Kyodain, and what they blew up weren't power stations but Restraining Bolts that were keeping them locked in human form, and now they're free to attack the planet. Gentarodoesn't take it well.
Law & Order: In the episode "Gov Lov" (the spelling is correct), Jack McCoy needs the husband of his male suspect to testify, but fears that the husband will take advantage of laws that allow spouses refusal to testify against each other. He's so determined to get the guy that he campaigns for, and succeeds in, nullifying all gay marriages in the state by reestablishing the "one man one woman" definition. It completely backfires when the husband admits, in a courtroom full of people, that he would have voluntarily testified against his husband, but now that McCoy had effectively ruined hundreds of marriages for his own agenda, he would refuse, even though he would be arrested for contempt of court.
The television adaptation of Terry Goodkind's Sword of Truth series, this trope is played at the conclusion of Season 1 and leads into Season 2 - although Big Bad Darken Rahl is defeated, Richard & Co have inadvertently "broken" the ground, opening a rift to the Underworld. Darken Rahl is revealed to have made a contract with the Keeper of the Underworld a while ago, and now serves as the Keeper's right hand man in his attempt to kill even more people than before. The Keeper, after all, hates all life. Darken Rahl also has the power to manipulate people even better than before - by offering dead souls the opportunity to live again if they agree to kill more people for the Keeper.
Also done earlier. Two of Rahl's soldiers have had enough of Rahl's tyranny and have the perfect opportunity to kill him, as one of them knows Rahl personally. Then come Richard and his crew and kill the one who was supposed to do the killing, assuming him to be a loyal soldier. Only Richard gets to kill Darken Rahl! Don't mess with the prophecy.
The Legend Of William Tell Vara, trying to escape from the group, falls over a cliff. When Will rescues her, she knocks his crossbow down into the ravine, leaving them defenceless.
Lexx: The destruction of Fire at the end of Season 3 leads directly to the destruction of Water, and then the subsequent flooding of Earth with the reincarnations of everyone who had been sent to Fire (Hell).
In the fourth episode of the original show, the cops stop taking bribes from and arrest the city's biggest crime lord. The remaining season and a half is spent trying to stop new, more ruthless gangs from getting a foothold.
In the fifth season, Ben thought that by killing Locke, he would be able to get back to the island, but that unleashes Jacob's nemesis. Ben then kills Jacob thinking he's being instructed by Locke, but has unleashed more terror again.
Not to mention moving the island at the end of season four. That resulted in rampant time flashes, and was the entire reason Locke had to leave the island in the first place.
Season 2 finale: Locke does a Heel-Face Turn and decides the button doesn't need pressing. Cue "I was wrong".
Malcolm in the Middle: In one episode, Reese was taught a lesson and gave up his bullying ways. This of course resulted in a bunch of lesser bullies turning the schoolyard into chaos and even abandoning standard ground rules, like not picking on the crippled kid.
Merlin: In the 1998 series, the titular character does this by recruiting Lancelot as the king's champion, who manages to completely screw up the relationship between the king and queen and provide Mordred with just the opportunity he needs to start a war and attempt to take over. All because he misinterpreted the Lady's message (who was, of course, unnecessarily vague) and assumed Lancelot was the knight he needed. Turns out it was his son Galahad. You know, the son who is now an orphan because his father abandoned him and his mother committed suicide.
In the 2008 version of the show, our hero, under the advice of others, kills Morgana for the "greater good". And although it's a Disney Death, when she comes back it's made clear that this action is a major contributor to Morgana - up till now depicted as a good guy - going to the dark side.
He also releases the dragon, even though it's clear the reptile is less than trustworthy.
Monk: "Mr. Monk on Wheels": A boy steals a bike, but then while riding off with it, hits a pothole, flipping himself over and sending him sprawling in the grass. Quite by coincidence, Monk and Natalie are walking through the office park when the accident happens, and Natalie, seeing the accident, walks over despite Monk's protests and helps the thief to his feet, even fixing the chain, and sends him on his way, this whole time unaware that the bike is stolen. Only once the legitimate owner of the bike comes running out of the nearby building does Natalie realize her mistake, and she is visibly embarrassed by this. It gets worse when Monk gets shot in the leg while knocking on the door of the thief's house.
Crow also has this reaction to the revelation the Planet of the Apes-esque Earth of 2525 they're orbiting at the start of the season is the result of Mike's descendants marrying simians.
Then there's the time Crow went back in time so Mike doesn't go into the temp agency. End result? Mike dying as he's rising to rock star fame and his Jerk Ass brother being shot up onto the Satellite of Love.
Once Upon a Time: A horrible example for Prince Charming. Trying to get water from a healing lake to heal the beloved of his unwilling fiancee Princess Abigail, he kills the siren guarding the lake. When his mother is mortally wounded, he goes back to the lake only to find that it's dried up because of the death of its guardian, and his mother dies.
While at war with a powerful alien race, a last desperate attempt is to carry a huge bomb to destroy their home planet. After finding and killing an alien in disguise, the heroes release the bomb and discover the alien turned the ship around—the heroes just bombed Earth.
Person of Interest: In one episode, an investigative journalist caused a man's death and put her own life in danger when she accused the man of being a criminal mastermind based on faulty intel.
Dr. K was being imprisoned unjustly by the government so they could use her as a researcher. She uploads a computer virus into their systems, and is apprehended by secret agents before she can install the firewall. The virus goes on to nuke the planet, wiping out pretty much all ecosystems, and either killing or enslaving every human not in the Domed Hometown of Corinth. Doctor K manages to escape thanks to some friends bailing her out. Nice job getting your freedom, doctor. Nice job protecting America, secret agents.
One of these in the backstory leads to the events of Power Rangers Ninja Storm. The main villain was initially just a power hungry ninja. His clan banished him from Earth. He came back as a power hungry warlord with alien technology. Oops.
And it wouldn't even have happened if Cam hadn't gone back in time and exposed said ninja as a traitor. It doesn't help that said ninja was his uncle.
Prison Break: Michael does this several times, but special mention can go to when he starts the riot at Fox River, leading to several deaths (for him to feel guilty about) and T-Bag finding out about the escape.
In "Pilot", Danny Matheson tries to prevent his father Ben from being taken by the militia. This results in one militia being killed, as well as the deaths of Ben and four villagers.
In "Chained Heat", Charlie Matheson persuades Miles not to kill a bounty hunter that has attacked the group. A few scenes later, said bounty hunter sics the Monroe militia on them.
In "No Quarter", the rebels hand over Miles Matheson to the militia when they find out that Miles helped to create the Monroe Republic. Subverted Trope, when they come to his rescue afterwards.
In "The Plague Dogs", Danny decides to rescue Tom Neville from being buried under a lot of rubble. He gets arrested again for his trouble.
In "Sex and Drugs", Charlie is given the job of murdering a former cop on behalf of a drug lord. Defied Trope, because Miles prevents her from doing the deed at the last minute.
In "Ties That Bind", Team Matheson decides to save Mia Clayton, Nora Clayton's little sister. Big mistake, because it turns out that Mia is a bounty hunter and mole for the militia. She gets the pendant from Aaron, and it gets delivered to Philadelphia, the Monroe Republic's headquarters.
Rachel's initial confession about the pendant in "Soul Train" ends up with a succession of Oh Crap moments for her in "The Children's Crusade" as she discovers just how single-mindedly obsessive Bass Monroe is. She could be considered directly responsible for the capture and torture of Dr. Jaffe and indirectly responsible for the capture of his daughter, since Bass apparently got the idea from capturing Rachel's family and thus spotting her weakness. In "Kashmir", she tries to construct a bomb disguised as a power amplifier. Unfortunately, she gets found out, and Monroe threatens to replace her with Dr. Jaffe. So Rachel kills off Jaffe to save her and Danny's lives.
In "Nobody's Fault But Mine", Team Matheson rescues Rachel Matheson and Danny. Unfortunately, Monroe now has a working power amplifier, which he uses to activate a fleet of helicopters.
In "The Stand", Danny dies stopping the helicopters. The Monroe Republic unfortunately gets more pendants, scientists and resources from Randall Flynn.
In "Ghosts", Miles and Nora manage to recruit Jim Hudson to their cause, but they wreck up his life in the process.
In "The Song Remains the Same", Charlie prevents Rachel from murdering Tom Neville. Tom Neville subsequently escapes and kills off the preacher Nicholas in the process.
In "Home", Captain Dixon tries to shoot Monroe, but he kills Emma Bennett and wounds Monroe instead. Miles kills him off without a word for that.
"The Night the Lights Went Out in Georgia" has Team Matheson stop a nuclear bomb from exploding in Atlanta, Georgia, and they make sure Georgia doesn't get to use the bomb. "The Love Boat" has Team Matheson rescue Dr. Ethan Camp (a scientist being made to produce smallpox for Monroe) and his family, and they make sure they escape somewhere where they won't be found. Unfortunately, those decisions come back to haunt them in "The Longest Day", when Monroe uses drones to kill off 270 out of 300 men in one drone strike.
In "Clue", Miles's decision to recruit Jim Hudson comes back to haunt him. The guy is still bitter about his life being wrecked up, he was responsible for the 270 men killed off, and he nearly kills off Miles before Jason Neville kills him off.
In "Children of Men", Rachel tries to be a suicide bomber on Monroe, but the attempt fails. As a result, she ends up bringing the Monroe militia and Randall Flynn into the Tower.
In "The Dark Tower", Team Matheson succeeds in turning the power back on worldwide. But it turns out that they played into Randall's hands, and he launches Intercontinental Ballistic Missiles at Philadelphia and Atlanta before shooting himself in the head. Not only that, but the American government he's working for is now going to return to the USA and retake what's theirs.
Kate tries to rescue her brother, and he ends up dead in her arms. It's worse than it sounds: she abandons the other outlaws who are ready and willing to help her, sneaks into the castle by herself, is captured in under five seconds, and watches her brother die as he tries to save her. And then for some inexplicable reason, the outlaws let this idiot join the team, giving her ample opportunity to endanger their lives in almost every single episode that follows.
In the episode "Too Hot to Handle" the outlaws steal Prince John's supply of water in order to help villagers struggling through a drought. Because they're all idiots, they donít bother to hide the water barrels that are clearly marked with John's insignia. When Prince John turns up and discovers the barrels in the middle of Locksley, he drowns a man in the drinking water. Thanks, heroes.
Everyone treats the mentally-unhinged Isabella like crap, and then they look surprised when she goes mad and starts killing everyone.
Nice job stabbing Brainiac with the knife from the Fortress of Solitude, Clark. You gave Brainiac a way to interface with the Fortress and release General Zod from the Phantom Zone.
Nice job releasing nearly a dozen other Phantom Zone prisoners, each of whom are equally as dangerous or possibly even more dangerous than Zod, during your own escape after Zod traps you there, Clark.
And of course, nice job simply splitting Davis Bloome and Doomsday apart instead of killing Doomsday, Clark. Did it ever occur to you that Davis would be just as violent and crazy as Doomsday and go on to kill Jimmy?
Our heroes woke up the Wraith, inflicting them upon the galaxy and angry because of the lack of "food" (humans). The Wraith were always bad news, but their newly accelerated schedule has resulted in many worlds wiped off the map, and everyone working on a way to stop them finding out they have a few decades less than they thought. Not that they stood a chance in hell, mind you, but they could at least have built up their populations enough to weather the culling.
Next is the Genii, one of those working on a plan to stop the Wraith, flawed though it was. Mistrust on both sides made them enemies for the better part of two seasons, up until a new leader came into power. All because they were trying to trade C4 as "farming tools"...
Then they turn a Wraith into an amnesiac human. He starts to turn back, but not all the way, and so once he remembers who he really is and escapes, he finds his people no longer want him now that he's half-human. By now, he's out to overthrow humans and Wraith and have the other human-Wraith hybrids he's created rule. He didn't hate humans that much, though, until our designated heroes betrayed him further, though.
Then they turn the Replicators against the Wraith... and the Replicators decide that the best way to fight the Wraith was to attack their food supply (of course, they may have done this out of spite because they already hated humans and Ancients).
In short, all three major threats to humans in the Pegasus Galaxy were created by the Atlantis team. They really, really should have just stayed at home.
It was even lampshaded when the combined peoples of the Pegasus Galaxy put Sheppard's team on trial for doing all of this, and call them out on every single mistake mentioned above. The trial, by extension, was to convict the Atlantis expedition as a whole, but they were smart enough to realize trying to tackle that beast directly was not going to end well.
The Ancients also did a good Neglectful Precursors work, as they accidentally created the Wraith, then developed the Replicators as a weapon against them. When the Replicators couldn't do the job, they wiped them out but missed some, hence their continued existence in the present. They shouldn't even have lost the war with the Wraith with the first place; they were too stupid to realize what "overwhelming odds" means and ended up giving their enemy the necessary tools to clone a massive army and Zerg Rush them into defeat.
Every time they defeated a Goa'uld, another, even more ambitious one rose to take his place in the resulting Evil Power Vacuum. This only stopped when the Goa'uld were overthrown as a whole.
Unfortunately, the SG-1 team wasn't content to rest on their laurels. Instead, they hunt down some old Ancient technology, get transported to another galaxy (sort of), thus allowing the Ori (evil ascended beings) to move in. In effect, after killing off the evil false Gods, the SG-1 team invited evil real "gods" to move in.
The basis for the franchise really. Movie - Unburied the gate, went to Abydos, unintentionally informed the Goa'uld that the gate on Earth had been unburied and thus Earth was within easy access for them. Killed Ra, everything is good. TV Series - Oh shit, you created a power vacuum. The goa'uld are fighting and they know the Earth stargate is unburied. And you've proved yourself to be a viable threat to their power and therefore put Earth in danger. Nice job.
Stargate Universe: The crew avoided making a mess for nearly a full season. Then after learning of a potential spy, they along with SG-1 alum launch a poorly-planned undercover mission that ends with Rush in the Lucian Alliance's hands. As a result of gaining his knowledge, they are able to connect the Stargate and there is now an entire enemy force on Destiny.
Kirk and company go to the Mirror Universe, and Kirk gets Mirror Spock to try reforming The Empire. So he does. When next we visit it, it turns out that the reforms made weakened the empire to the point of being unable to defend against the Klingon/Cardassian Legion of Doom. Humans and Vulcans are now slaves. Way to go, Jim. (This gets Retconned into the Expanded Universe as Spock playing out a really longBatman Gambit; he could have made reforms without weakening the Empire, but he didn't believe they'd last beyond his death.)
The Devil in the Dark. Turns out that monster you shot? It was an alien nanny who was only acting in defense of the nursery. And those weird stones that you've been trying to crack open? They're the babies.
At the start of the episode "The High Ground", Doctor Crusher uses her Doctor's Orders to demand to stay at the scene of a terrorist bombing to help, in spite of the dangers it presented. Naturally, she's quickly kidnapped, setting in motion events that nearly sees the Enterprise destroyed, almost brings the hammer of the Federation down on the planet, causes the deaths of several crewmen as well as the Well-Intentioned Extremist terrorist leader, and does nothing but add to the already unstable political climate of the planet they're on. Yay morals?
At the end of season four, Sam spends most of the season getting the power to kill Lilith so he can stop her from breaking the final seal and freeing Lucifer. In actuality, Lilith was the final seal, and by killing her he causes the release of Lucifer and kick-starts the Apocalypse. Oops.
At the end of Season six, Castiel absorbs the monster souls of Purgatory to get the power to defeat Archangel Raphael, who wanted to restart the Apocalypse. But in doing so, he unleashes the Leviathans, creatures that God locked away to stop them from eating everything else.
To an extent, Dean as well, not only for breaking the first seal between seasons three and four, but also for revealing to Azazel that his plans were going to work before he'd even put them in place. Okay, so Azazel was possessing his grandfather at the time and Dean thought he was going to save his mother. Ironically this caused the death of his grandparents, the death of his father, and the resulting deal that in 10 years Mary would allow Azazel into her house for her son in exchange for resurrecting John.
This seems to be a problem in the hunting profession in general, as hunters' involvement in Metamorphosis (4.04) and Citizen Fang (8.09) just lead to their deaths, and in the first case, caused the rougarou to have his first taste of human flesh and transform completely. Oops.
Teen Wolf: Scott is well-meaning in his desire to help Jackson and does not want to kill him or let Derek do so. However, by protecting Jackson, he technically bears some responsibility for the murders that Jackson subsequently commits as the Kanima, including a fair-sized chunk of the Beacon Hills Police Department.
Titus: Subverted Trope in the episode "Titus is dead". After the main character finds out that his dad who has been divorced five times is dating again, he tries to convince his dad to break up with his new girlfriend. After talking to each other, Papa Titus proposes to his new girlfriend, instead of breaking up with her. Nice job fixing it hero.
Generally speaking, the problem in any given episode was probably caused by them at some point:
On Gwen's very first day on the job, she tossed a screwdriver, accidentally breaking open an alien meteor and leading to the deaths of Carys' friend and ex-boyfriend as well as an entire sperm donation centre.
Two people were killed and the whole planet was put in danger because Ianto secretly stashed his Cyberman girlfriend in the basement.
In the episode "End of Days", Owen Harper's opening of the rift rescued his boss and his best friend from being trapped in the wrong decade forever, but it also caused a wave of anachronisms including ancient soldiers in the streets and an outbreak of the bubonic plague in Wales. This despite Ianto practically begging Owen not to open the rift, and even shooting him to try to prevent it. Instead of learning from this colossal mistake, the rest of the team eventually side with Owen and do the exact same thing, again, to flush out the results of the prior opening. Which works, but unleashes Abaddon. Predictably, things get worse before they get better.
Not to mention how it nearly killed everybody in "Dead Man Walking" and did kill 12 people.
All those problems with Captain John Hart would have been avoided if it weren't for Jack simply being there.
In "Children of Earth", Jack and Ianto have gone storming into the alien's base guns blazing in order to, erm... threaten it, pissing it off enough to release a deadly virus, killing everyone in the building, including Ianto.
The really hilarious irony being that Torchwood was originally founded by Queen Victoria because she felt that the Doctor brought too much trouble in his wake!
Touched by an Angel: A man wakes up from a twelve-year coma. He got in a car accident because he used his wife's car instead of his own. He got in his wife's car because he couldn't find the key for his own. He couldn't find the key for his car because Monica was holding it so she could look at the angel keychain...
Nice job not keeping your mouth shut JUST to try to prove that Beck got his line right, Tori. Too bad it made the Jerk Ass lead star not approve of you or him.
And in "Locked Up", when the chancellor is about to free Tori, Robbie knocks his electric clock into his octopus' tank, which zaps it and kills it. And then they're all in prison with her.
Although, Tori does end up fixing things. She (accidentally) gets the Jerk Ass lead star hospitalized, which not only gets Beck his role back, but also makes everyone else on the set happy because they all hated her.
On The Voice, judge/coach Seal came down hard on contestant Kiyomi Vella for having a "backup plan" in case her musical career didn't pan out (Vella was attending university to get an environmental science degree, something that would give her an income while she pursued her musical dreams). The scolding shamed Vella so much that she quit college to concentrate on music at his urging. And then she was eliminated from the competition. As of this writing, neither her musical career, nor her attempts to get back into college, has been all that successful. Good job, Seal. Really good job.
The Walking Dead: Michonne killing the Governor's zombified daughter. Whether you think his and Milton's attempts to try and heal her were futile or not or whether you think he deserved it or not for kidnapping Glen and Maggie; the fact remains that beforehand the Governor was far closer to a Shane-style villain. Killing others to secure their stuff, interrogating people using violence etc. Afterwards however he became a full on psychotic Bond-villain that eventually leads to the deaths of Merle, Andrea and about a dozen Redshirts