In "The Starzl Mutation", Shawn receives a cigar as a wedding present from Claudio Borghi but it is no ordinary cigar. Claudio, who disappeared in 1961, has the ability to induce visions of possible futures in the people that he touches. As he prepared the cigar himself, it contains his ability. When Shawn smokes it, he sees two visions of the future. In the first possible future in which he married Isabelle, Richard turned the 4400 into an army and launched a preemptive strike on the general public. Instead of helping Isabelle to get in touch with her humanity, Shawn was corrupted by her influence. He uses his Harmful Healing ability to kill Richard and takes pleasure from the experience. In the second possible future in which Tom talked him out of marrying Isabelle, the catastrophe that the people from the future hoped to prevent has come to pass. Shawn frantically brings Tom back from the dead, clearly not for the first time, but he only remains alive for a brief period. Everyone else that they know and love is dead.
In "Try the Pie", Maia begins Dreaming of Things to Come, which is not the normal way that her ability manifests itself. She sees herself, the rest of the 4400 and everyone who is promicin positive being rounded up and sent to an internment camp, possibly even a death camp. From a prominent photograph of him at the camp, it is determined that Gabriel Hewitt, a member of the Seattle City Council and a candidate in the mayoral election, is a senior figure in the government in this potential future but it is unclear whether is the President, the Vice President or a Cabinet member. Diana is concerned that Shawn running for the City Council may be providing Hewitt with a platform for his anti-4400 views, thereby unintentionally giving him the political capital that he needs to make this future come to pass.
In Agents of S.H.I.E.L.D. Season 5, Team Coulson are sent 74 years into the future, and find that Earth has been totally destroyed, with all that's left being a crescent that barely has an atmosphere and is overrun with alien predators. What remains of humanity is packed onto a crowded space station, where they've been enslaved by the Kree. Complicating matters is the implication that it's actually a Stable Time Loop, that the team's efforts to undo the future are in fact what leads to it occurring. Fortunately, this turns out to not be the case, but one dose of Centipede Serum in the wrong place is the difference between Earth remaining intact and the real Destroyer of Worlds - Talbot, having turned into a batshit insane Dark Messiah from a mixture of brain damage, guilt over betraying S.H.I.E.L.D., and Gravitonium infusion, the last of which merely exacerbated existing Sanity Slippage - turning it into an asteroid field and the aforementioned crescent.
ALF episode "Future's So Bright, I Gotta Wear Shades" has Alf thinking on his own future once he realized he will live up to 200 years and wonder who would he live with. All his visions are nightmarish including; living with the already senile Willy and Kate to the point he chooses to surrender himself to the US government, living with Lynn and his boyfriend who are mimes and use him in dangerous circus performances, living with an adult Brian who is married to a mafia boss who hates him and treats him as a pet until she decides to execute him and finally with Eric who as an adult is the host of a children's show and uses Alf as a living puppet. Of course, once he tells all these fantasies to the Tanners, Kate clarifies that no member of the family would ever treat him like that.
About halfway through season 2, Trance Gemini swaps herself for another her from a bad future, who has come to help avoid making the same mistakes that led to her bad future, although by doing so, she might as well have made things worse.
Season 7 of Arrow has a parallel storyline taking place in 2040, where Star City is once again a Wretched Hive, with gangs running everything outside the Glades and corrupt politicians and cops just care about their own pockets. The key figures of this storyline are William, his half-sister Mia, John's adopted son Connor, and Zoe. They get a chance to change this future by somehow ending up in 2019 and working with the original Team Arrow.
Buffy the Vampire Slayer has a partial example (bad, but not exactly the future) in the Season Three episode "The Wish". Cordelia's wish for Buffy to have never come to Sunnydale is granted by a spirit: Sunnydale's population lives in terror of the vampires, Xander and Willow are bloodsuckers (and particularly brutal ones, at that), Oz and Giles are members of a ragtag and badly outnumbered resistance, The Master is still around, Angel is his mentally broken prisoner, and a now Cleveland-based Buffy is a rude, apathetic jerk. The episode ends with all the above (including Cordelia!) dead but for Oz, Giles, and The Master before Giles can undo the wish.
The future that Chris comes from in Charmed. An earlier episode has the sisters use an embarrassing spell on a Jerkass guy for his dog's actions. Then they end up in the Bad Future as their older selves and see that this one act has resulted in the guy revealing the existence of witches and becoming a powerful politician winning on the platform of Burn the Witch!. One of the sisters is accused of murdering a Muggle with magic and sentenced to death by fire. Worse, as they find out from a security footage, she actually did it. In the end, the guilty sister chooses to allow herself to burn as punishment for her crime. This future is, presumably, averted after all three return to their time and undo the spell on the Jerkass guy.
Chou Sei Kantai Sazer X starts off with one. In 2005, a band of space pirates managed to take over earth. A flash forward to 2500 shows the earth being covered by dark red skies and the last pockets of human resistance living in hidden underwater bases. The series itself focuses on three heroes from said future traveling back to 2005 to prevent said future from happening.
The "Remedial Chaos Theory" episode of Community has an alternate timeline in which Pierce is dead, Annie has gone insane, Jeff's lost an arm, Shirley is an alcoholic, Troy lost his voicebox and Britta has a blue streak in her hair. Things got dark.
Danger Five's second season ends in an alternate timeline where Hitler won World War Two, after a time travelling mishap in the second-to-last episode. In a rare version of this trope, there seems to be no way to return to the default timeline, and Danger Five have to make do in the Bad Future. Once they finally kill Hitler, though, everything seems to work itself out.
While it isn't quite a traditional Bad Future story, Season 2's "The Dalek Invasion of Earth", the sequel to the first Dalek story, has just about all of the standard features of one. It showed a 22nd century Earth ruled by Daleks. This has gotten enshrined in the Whoniverse as the 22nd century, but the later "Day of the Daleks" showed another 22nd century dominated by Daleks, which did get undone. (The "Day of the Daleks" future happened following a nuclear war in the 20th century.)
In "The Space Museum", because of a malfunction in the TARDIS, the Doctor and friends see their own dead bodies preserved in the Morok Empire's eponymous museum, then spend the rest of the serial trying to prevent that from happening.
"Inferno" combined elements of Mirror Universe with Bad Future, except in this case the Doctor has ended in a Mirror Universe just a little bit further ahead in time, too, meaning that he knows what will happen in his world.
In several stories, the Doctor shows why they can't just leave even if they have seen the future. They have become part of events and need to see them through. This is first done in "Pyramids of Mars" when Sarah Jane says they can leave 1911, where Physical God Sutekh is about to break free, as they know the world wasn't destroyed in 1911. The Doctor takes her to 1980 and shows the world has been destroyed as they weren't there to stop Sutekh, therefore they need to go back and stop him.
"The Curse of Fenric" has the Doctor claim half a million years of industrial progress has led to a polluted world where humans have evolved into Haemovores, aquatic Vampires. The Doctor convinces the final Haemovore to avert a Stable Time Loop in poisoning the seas and instead destroy Fenric. However it is left unclear if this future has been averted or staved off. He does, however, explicitly prevent the destruction of our Earth in the 20th century.
"Turn Left": Donna has an alternate timeline created around her where she never met the Doctor and he dies underneath the Thames. Without him around to stop several crises, the Earth gets worse and worse. Southeastern England is flooded with radiation, and the UK gradually turns into a fascist state.
"The Girl Who Waited" has Amy Pond accidentally get trapped in a faster time stream on Apalapucia. By the time the Doctor and Rory get to her she is 36 years older. They are able to rescue Amy 36 years previously, at the cost of the older Amy allowing herself to be erased from existence.
"The Name of the Doctor" has the Doctor visit his grave on Trenzalore, a planet devastated by his final battle. This timeline is averted when the Doctor tweaks his (apparent) resolution to the Time War, sealing the Time Lords in a parallel universe instead of destroying them, in "The Day of the Doctor". They return the favour by granting him a new set of regenerations as he is dying on Trenzalore in "The Time of the Doctor".
Dollhouse's season-concluding Epitaph episodes show us the logical conclusion of the brain-warping technology.
"Epitaph One": To put it simply, if you get too close to any form of technology, there is a good chance you will be affected by a "signal" that wipes your memory and imprints you with simple orders to "kill everyone who isn't programmed to kill everyone." That's not even the worst part.
"Epitaph Two: Return" and the end of the previous episode establish that the Bad Future is the canon ending of the series, and even after Topher's Heroic Sacrifice to restore everyone's original minds, the world is still a post-apocalyptic Crapsack World. And the weaponized Dollhouse tech is still out there....
Double the Fist shows us one in the second to last episode where Steve has taken over the world and punishes people for being weak (which entails such things as reading and being comfortable) and uses Womp as the symbol of Weakness. Subverted in that this future apparently comes to be, and that within the context of the show, this is a good thing.
The Flash (1990) had a particularly contrived version of this, in which a villainous motorcycle gang leader became mayor of the city and somehow turned it into a repressive dystopia.
The Flash (2014): The Wham Shot at the end of the pilot reveals that ten years down the line, the Flash will end up disappearing while fighting a crisis that turns the skies red. Dr. Wells is either from this period, or somehow knows about it, and seems to be manipulating Barry to bring it about. In Season 3, Barry travels to his own future and discovers that in grief over Iris's death, his future self has quit being a hero, allowing meta-criminals to take the streets, Cisco has lost his hands (and powers) in a fight with Killer Frost (who is permanently evil), and Barry and Joe haven't spoken in years. Barry inspires his future self to try to rebuild Team Flash and go back to heroing, although it's all moot, as he manages to avert this future, when HR makes a Heroic Sacrifice to save Iris, and Savitar is erased from the timeline.
Season 3 finale. The Alternate Universe got destroyed, but instead of saving ours, it only makes things worse. Walternate is somehow alive and wants to destroy our universe as a revenge. Even opening credits become gray for this occasion. The opening credits also include things that are at the cutting edge of science. The title sequence for this episode includes things like hope and water.
The end of the 4th season is even worse. How worse? The intro lists Joy, Individuality and Imagination amongst similar themes as fringe sciences. Unlike previous one, this appears to be a legitimate flash forward, without any sort of Reset Button hit. It's hit in the series finale, but that takes a Heroic Sacrifice from Walter.
Full House has an episode were the guys imagine how their elderly lives would be if they keep spoiling the girls. It shows them all single, old (and in the case of Jesse bald) and maybe senile getting bullied by all the girls who despite being adults still live with them and have pretty much the same spoiled girl behavior.
Game of Thrones: Dany gets a glimpse of this in the House of the Undying. The Red Keep is in ruins, winter has come (and hasn't left for a long time), everyone's dead, and snow sits on the Iron Throne. This premonition also shows up in Bran's visions later on, implying it's a demonstration of what will happen if the White Walkers overrun the entire continent.
However, as the end of the series shows, the vision Dany saw wasn't of what would happen if she lost. It was what would happen ifshewon.
Heroes, "Five Years Gone," after New York was blown up, and Sylar takes over the country. And then again, with the Shanti virus having wiped out most of humanity. Season Three starts off apparently averting one Bad Future and creating another, eerily similar to the Bad Future they prevented in Season One (minus the New York explosion).
Kamen Rider Zi-O is about a group of time travelers coming back to stop the protagonist from growing up into an Evil Overlord who rules the world with an iron fist. One group of travelers wants to stop him by either killing him or ensuring he becomes a hero instead, while the other group thinks this future isn't bad enough and wants someone even worse to take his place.
Legends of Tomorrow is all about a disparate team of C-List heroes and a couple of Card-Carrying Villains being recruited by a man from the future trying to stop Big Bad Vandal Savage from conquering the world by the second half of the 22nd century. The pilot actually opens here, with a scene of Savage's forces annihilating London in the "Second Blitz", and the episode "Leviathan" sees the team actually travel to this period and get a first hand look at Savage's conquest.
And every time that the team messes up a mission, they're shown how the consequences might result in an even worse future, until the heroes manage to undo the damage and prevent it from occurring — in part two of the pilot, after Savage gets his hands on a piece of Ray's ATOM suit, we see a future where he reverse engineers the technology and accelerates his conquest to the point that Central City is shown burning in 2016. In "Fail Safe", after Prof. Stein is captured by Savage and his Soviet allies, we see a potential future where they force him to share the secrets of the Firestorm matrix, resulting in an army of Soviet Firestorms winning the Cold War and conquering America by the turn of the century.
During the sixth episode of the series, they also crash-land in the 2046 version of Star City, the main setting in Arrow. All of the main cast of that show except for Oliver and Felicity have been killed off, and the city is reduced to a bunch of ruins ruled by criminal gangs, united under the leadership of Grant Wilson, the second Deathstroke. Oliver has crossed the Despair Event Horizon while Felicity has long since left the city as it was considered a lost cause. The team help Oliver and the new Green Arrow, Connor Hawke, overthrow Grant and begin to retake the city, before they leave. And Rip repeatedly points out that this is just a potential future, that will probably be undone when the team return to their own time.
In "Progeny", the team travels to 2147 in an attempt to sabotage one of the key events leading to Savage's rise. In this time, corporations have supplanted all governments, and outside the Kasnia Conglomerate (which is only stable because it's a Police State) that controls Eastern Europe, the world is an overpopulated, poverty-ridden mess (there are repeated mentions of food riots). And in just five years time, Kasnia will come under the control of a dictator loyal to Savage, who will unleash a virus that will decimate the world's population and leave it ripe for Savage's conquest. And the team's attempt to stop this just makes it happen sooner.
In "Destiny", the Time Masters reveal that the reason they're allowing Savage's conquest of the world (and in fact are aiding it) is because they've foreseen that in 2175, the Thanagarians will invade Earth, and being united under Savage is the only way the planet will survive. Though Rip is quick to point out that a world ruled by Savage is not a vast improvement.
Season Two is all about the team preventing abberations in the timestream caused by rogue time travellers, the consequences of which will usually result in a Bad Future. For example, in "Abominations" an abberation will cause the South to win the American Civil War, and in "Outlaw Country", one will cause a future where outlaw Quentin Turnbull will use dwarf star alloy to take over all of the United States west of the Rockies. In "Doomworld", the Legion of Doom uses the Spear of Destiny to create a world, where Team Flash and Team Arrow are dead, the Legends have been given menial jobs or serve the bad guys, Darhk is the mayor of Star City, ruthlessly eliminating any opposition (and has his powers back), Thawne runs S.T.A.R. Labs and is hailed as the world's greatest scientist, Merlyn has his family and hand back, and Snart and Rory can rob any bank in Central City with impunity (Snart owns them all anyway).
The Flash Forwards on Lost are fairly dystopian, with characters hallucinating (maybe), trying to commit suicide, being killed, and going crazy. Unfortunately for them, all of the flashforwards have now happened in the present, making this Bad Future the canonical bad past in the show's current present time.
The ending of Mad About You is not as bad as most examples of this trope, but does depict a future where Jamie has a spontaneous abortion (making Mabel only child), and Paul and Jamie get divorced (for a while).
This is where Matt Anderson comes from in Primeval. He came back to the present to try to keep it from happening. Before that, Helen Cutter tries, in her own way, to prevent one from happening, except her attempts, including killing her husband who has just saved her life, are likely to make things worse.
Played with in the penultimate episode of Person of Interest. The Machine presents simulations to Harold Finch showing what would have happened if he had never built the Machine. At first it appears this alternate future is no better or worse than the current one — some friends who've died during the series live and thrive, while others who have found redemption through Team Machine continue on their dark path. Then it's shown that without the Machine to oppose it, Samaritanwas built anyway and is well on its way to taking over the world.
Red Dwarf uses this trope at least once in series 6, episode 6 (Out of Time) where the crew meets their future selves, refuse to become them, fight them, and are blown up by them. The series also inverts the trope once in series 1 episode 2 (Future Echos) and subverts the trope in Series 2 episode 4 (Stasis Leak). It was also used in the first episode of Series 7 (Tikka to Ride). There, by accidentally preventing the Kennedy assassination, they create a future where J. Edgar Hoover became president - and ended up in the Mafia's pocket. The end result was an America under nuclear threat where all major cities (or at least Dallas) were deserted.
Sanctuary, Pavor Nocturnus. Though it's likely to have been just a fabricated illusion.
A short-lived version pretty much every episode in Seven Days. Basically, Parker's job is to go back in time to the previous week and prevent something horrible from happening. Several episodes involve chrononauts from years in the future claiming that they have been sent to prevent a long-term example. As it is, we only have the word of the chrononauts that this is the case. One of them is determined to kill a female scientist who is supposed to discover the Cure for Cancer, which will mutate into a global plague. Another wants to assassinate a Muslim religious leader to prevent him from plunging the world into a new wave of terror (this one turns out to be a demon of some sort trying to create a bad future).
Sleepy Hollow: Throughout the back half of Season 4, there are repeated vision glimpses of a future in which Malcolm Dreyfuss, having become immortal and gained control of the Four Horsemen, has conquered the world, crushing all resistance, ruling as a tyrant, and keeping Ichabod imprisoned to torment. This comes into play in the final episodes, as Malcolm's lieutenant Lara (a future version of Molly) has a Heel Realization and travels back in time to stop this from happening.
Smallville has a future ruled by Zod, which Lois visited between Seasons 8 and 9, and which we finally saw in "Pandora".
Stargate Atlantis had an instance of this in the fourth season finale "The Last Man". Due to a freak solar flare, Sheppard went 48,000 years into the future where a hologram of Rodney informed him that due to his disappearance, the expedition fell apart and "Michael" took over the galaxy. To set it right, said hologram predicted when a similar flare would occur and sent him back a few days after his accident.
Stargate SG-1 has the paired episodes '2010' and '2001'. The first takes place entirely in the bad future, with them eventually sending a message back to the 'present'. It looks like they succeeded, but then two seasons later they run into the same bad guys again, fortunately someone remembers the old warning they got and that it might have been in reference to these new potential "friends". History looks like it's starting to repeat, but SG-1 recognises the threat and averts it.
It says much about the Stargate Command personnel that, when a note written in Colonel O'Neill's handwriting and splashed with Major Carter's blood comes out of the Stargate warning them of a Bad Future if they make contact with a particular planet, they immediately take that advice to heart and lock the address out of the system without needing to see for themselves.
Played with in "The Visitor". The future depicted is a rough one for the Sisko family, but compared to what happens in the subsequent seasons, it's arguably a better future for the Alpha Quadrant as a whole.
"Children Of Time" has a variation by way of a Timey-Wimey Ball. The Defiant crew encounters a colony made up of their own descendants, created from a Bad Future in which the Defiant was thrown back in time 200 years, leaving them stranded in the past, permanently cut off from their families, and causing Kira's premature death. The rest of the episode revolves around them trying to decide whether to save themselves, thus erasing the colony and its inhabitants from history, or to give up their own lives and futures to let the same sequence of events play out.
In the series finale "All Good Things..." Picard jumps between the day he took command, the present, and twenty-five years into the future. The future isn't a strictly-speaking bad one for most involved (Crusher captains her own medical ship, Data has Isaac Newton's old job and a few dozen cats), but Riker and Worf now hate each other thanks to Worf starting a relationship with Troi just before Riker was going to try and get together with her again—and then Troi died in unspecified circumstances. Present Picard ignores the usual prohibition on discussing the future to share these details with them in hopes of preventing these estrangements.
A cast-centric variation in the episode "Timeless". Voyager has crashed on an ice planet killing the entire crew except for Chakotay and Harry Kim, who try to Set Right What Once Went Wrong. However there's nothing else wrong with the future, so Geordi LaForge, a main character from Star Trek: The Next Generation, is trying to stop them.
Likewise in "Shattered". Voyager is split into past and future timelines which Janeway and Chakotay must pass through to solve the problem. The problem is that this Janeway is from before she destroyed the Caretaker Array, so from her perspective everything she sees is a Bad Future. Chakotay has some trouble convincing her not to Screw Destiny and Set Right What Once Went Wrong.
The future in "Endgame" is a Downplayed example. Voyager successfully returned to Earth, but the journey took over twenty years, Seven of Nine died, Chakotay is implied to have suffered Death by Despair as a result of Seven's death, and Tuvok went insane from a disease that was untreatable in the Delta Quadrant but treatable with a compatible Vulcan. Although most of the crew seems relatively happy, Janeway is so distraught over these losses that she arranges to go back to Set Right What Once Went Wrong.
Prior to the events of season 2, Spock encounters a being called the Red Angel who shows him a vision of the future. In this vision, a rogue AI called "Control" destroys all sentient life in the galaxy after upgrading itself with data currently stored on Discovery. Ultimately, the solution is to send Discovery into the distant future, stopping Control's plans and preventing this apocalypse.
Season 3, however, reveals that while galactic omnicide was prevented, the 32nd century isn't exactly hunky-dory. Discovery arrives to discover that a catastrophe called "The Burn" neutralized dilithium throughout the galaxy, destroying millions of warp-capable starships. As a result, The Federation collapsed from 350 member worlds to just 38.
The Supernatural episodes "The End," reveals that, five years in the future, the Croatoan virus has turned almost everyone into violent, zombie-like killers, the United States is a veritable wasteland under Martial Law, Lucifer has gotten his perfect vessel and taken over, and Sarah Palin is President. Castiel's fallen, is sleeping with any woman he meets, as well as taking drugs. Bobby's dead. Sam said yes to Lucifer. Dean's a bastard who sacrifices his friends. By the end, future!Dean, future!Castiel and Bobby are all dead, with Lucifer pointing out that it will always end here and he will always win. However, because Dean was sent there by an angel who clearly had ulterior motives, it has been suggested that Dean was instead sent to a Pocket Dimension designed specifically to convince him to take the offer to become Michael's vessel.
Years and Years: One of these gradually emerges over the course of the show, with society getting more and more unstable and oppressive. It begins with Trump nuking one of China's artificial islands and things only get worse over the course of one Time Skip after another. Russia takes over the Ukraine, the Arctic completely melts, a banking crisis dwarfing the 2008 recession occurs, Spain is taken over by communists, Greece leaves the EU and Mike Pence becomes president of the United States and removes LGBT, immigrant and reproductive rights. Britain, in particular, has to contend with a refugee crisis, 80 straight days of rain, an outbreak of 'Monkey Flu,' major power outages caused by cyberattacks and dirty bombs going off in Bristol and Leeds. This reaches its peak with the ascension of Vivienne Rook's far-right populist Four Star Party, which proceeds to crack down on political opponents, abolish the BBC and open concentration camps where displaced individuals will be allowed to die to reduce crowding. Fortunately the ending implies things are going to get better.