Abstract Apotheosis: The Minor Arcana Alicorns are all this, being mortals who became Concepts. The Magician Alicorn (Dark World Twilight) and the Draconequus of Cruelty (Dark World Fluttercruel) did this as well.
There's Derpy's biological mother, who tried kill her when she was just a foal.
Accidental Pun: Luna's filly alternate self who plays with Pip is called Moonlight. That is, she's moonlighting as a normal filly. Word of God is that this was completely unintentional.
Likewise, the fact that Discord turned Blueblood into a literalDefrosting Ice Queen (well, Princess), which lead to him fulfilling the actual trope, has been said by Word of God to be accidental.
Achilles' Heel: Turns out the Eldritch Abominations imprisoned in Tartarus are vulnerable to a mixture of the blood of a member of Nature's Law and Nature's Fury due to rejecting existence. This also strips them of their immortality and lets them be destroyed, which the one Celestia and Luna fought found out too late.
Makarov's is that his powers weaken if he's enraged or taken off guard, as well as the fact Shining Armor is Immune to Fate.
Changelings have a number of these. The biggest is their armor is great against sharp weapons, but, while not shattering, is weak against blunt force. Their mind control magic can also be universally broken by a loved one showing their victim love while aware they're brainwashed. Their magic is also linked to their lifeforce, so should a Changeling run out of mana/love, they die.
Chrysalis herself's primary weak point is she's a love guzzler and burns through her stores rapidly, though that hasn't come into play yet.
Trixie's mother, Morgan actively defends Hoofington from Princess Gaia's army. and, from what we see, is a pretty powerful Unicorn when she fights.
Derpy Hooves defending her daughter from Princess Gaia's forces, anyone?
Despite being insane, Screw Ball/Golden Tiara certainly counts. Breaking out of the heavily guarded insane asylum she's kept in is childs play for her the first time. The second time when her Mama Bear side finally kicks in? She not only kicks everypony's flanks who tries getting in her way, she kills a Cockatrice and a Timber Wolf bare hoofed!.
Actually a Doombot: In 15 Part 2, after getting a beatdown by a supercharged Princess Cadence, then shot in the head by Dima, it's revealed that Makarov was a robot. Justified, as it's implied it was Makarov until he was shot and he just used his powers to put a robot in his place at the last second.
Happens on both sides when Chrysalis and Cadence face off for the first time. Cadence was using an Avatar while Chrysalis was using one of her minions infused with her magic as a puppet body, neither of which being revealed until after the fight is over.
The G1 My Little Pony series pony, Mimic. What is she like in this timeline? The only mortal pony to ever injure Discord and the reason he's missing that tooth by kicking him thousands of times in the face at the speed of sound! Sure, she died horrifically afterwards, but give the girl some credit!
G3 Pinkie Pie, Thistle Whistle, Sky Wishes, Star Catcher, Wysteria, Rarity, Spike, and Minty, though all of them had to Take a Level in Badass. Everyone but Pinkie and Minty managed to give Strife, a Physical Goddess and Reality Warper on par with Discord, a run for her money and actually scare her at one point. Pinkie and Minty beat Luna, though she was weakened at the time, she was still a powerful Physical Goddess at the time. Oh, and Star Catcher was mortal incarnation ofCelestia.
While Canon!Cadence turned out to be pretty badass herself, this universe's version managed to fight Havoc's avatar! with an implication she actually won. It's not yet been explained how the present Cadence came to be, however.
The Love Cats from the IDW Comics. While in the comics they were wiped out by the Changelings, in this version they come along with Luna's guard as back up and kick flank. Pinkie Pike style. Justified in that it's explained by Pinkie (who may apparently one day become their deity) that they didn't know the Changelings were a threat in the comics while here they do.
Adorkable: Luna is this a good bit during her second sidestory.
While just another bullet in a long list of horrors, Trixie fighting her awakening as an Element of Magic laser targets that special nerve of paranoia and fear for those who those who ever had to deal with that sort of emotional crisis forwhateverreason.
There's also the fact that Rainbow Dash now fears Scootaloo's real parents will come and take her away from her.
Bright Eyes' Gaiden Story contains a lot of this, particularly from Lancer's perspective. His wife lost his memory, forgetting who he is and their time together and, as a result of a complete accident, he has to live in constant fear of her being lynched for the disaster with the possibility of ponies taking Revenge by Proxy on their children (which almost happens on the day his second child is born).
There's also Bright Eyes' recovered memory of being lost in the woods as a filly and nearly being killed by a pack of coyotes while her parents had no idea where she was. Thank goodness that deer spirit showed up when she did...
Dark World!Fluttershy's entire situation in "Fluttercruel's Punishment". No matter how much she wants to protect her daughter, others rightfully desire to punish the child for her crimes. In the end, Fluttershy is forced to admit her daughter was a psychopathic Serial Killer and a monster who harmed others, and allow her to be punished for her crimes.
Affably Evil: Princess Gaia is a polite, gentle, and friendly host to the Mane Cast. Of course she is still Fluttershy after all
Havoc, Entropy, and the Father all take disguises during Starlight's Trial, but none of Them seem to be doing it for this reason. Havoc is doing it to appeal to Starlight's pride, the Father is likely doing it out of fairness (since His true form would likely reveal He was on Starlight's side), and Entropy because...Havoc drug Her there and made Her do it.
According to Word of God, the courtroom from Starlight's trial (actually the realm of Judicium, the Alicorn of Judgment) was an example of this trope.
Afraid of Needles: Twinkle Shine is apparently terrified of needles, when the Shining's group needs to get vaccinations before arriving in Zebrafrica she is clearly hesitant to get hers, and apparently ran away at some point during it. Shining himself also seems to have this fear as well, though he at least has good reasons why. According to Godzillawolf, the beta reader who suggested the joke, he did it as a Take That Me to himself, as he's this trope in real life.
After the End: Turns out the present world is the result of a Class 2 Apocalypse of the G1/G2 world. Pony POV Series Gaiden: Seven Dreams/Nightmares takes place in this world.
The Dark World Arc probably counts as well, seeing as Discord's ruled the world for a thousand years.
The Ageless: Celestia and Luna, though they actually have Nigh Invulnerable immortality. Everypony in the G3 world had this, however, thanks to an ancient spell. Unfortunately, giving birth to Star Catcher broke the spell on her mother, Star Maker, and resulted in her aging and dying while all around her remained the same. Pinkie was included in this, but its safe to assume she's lost it.
A God I Am: A number of villains have this mentality with the Valeyard being on a Time Lord Victorious power trip. However, only Chrysalis has this as her explicit end goal, desiring to become complete and turn into an Alicorn. However, when she finally succeeds, it turns out that there's a good bit more to divinity than just power, and she's force to grow a heart by the Elements of Harmony as part of the process, resulting in her having a mental breakdown.
Alas, Poor Villain: Destruction. Despite being literally addicted to destruction, he was also the most sympathetic of them, as he hated his addiction and wished he didn't have it at all. His desire in the war was to cause so much destruction he'd finally be rid of it once and for all. Him being killed and eaten by his own brother is extremely tragic.
Kind of hard not to feel sorry for the Master in the Dark World, who the Valeyard subjected to the same thing Discord did. What's worse, according to Word of God, the Valeyard's claim to keep killing him until he gets a good personality was just an excuse to kill him over and over again.
Despite spending a thousand years massacreing entire families with no remorse, following Discord's orders without protest, and generally being the biggest Jerkass in the Dark World, It's pretty hard not to pity Angry Pie when Twilight gives her a HUGE No-Holds-Barred Beatdown in "Cold Hoof Blues". By the end of the chapter, Angry Pie is crying and begging her foals to forgive her for failing to succeed in her task to bring them back to life. Even the other heroes (whom Angry Pie just tried to kill) are shocked and horrified by Twilight's actions.Thankfully, they manage to talk Twilight down and she ultimately redeems Angry Pie with a reverse Memory Spell (showing her Twilight's memories instead of her own).
Similarly, it's hard not to feel bad for Dark World Fluttercruel, even after all she's done, when she watches Discord get literally stabbed in the back by Rancor, which she simply cannot comprehend. She ends up crying and pleading with Discord to absorb her to heal himself. It shows that despite all else, she's still a foal who deeply loves her father and doesn't want him to die. What's she like by the end of the final fight with her? A broken little child who by that point knows her actions were wrong but is too driven by her Undying Loyalty to her father to make a Heel-Face Turn.
Dark World!Discord as well, who wanted nothing more than to save Fluttercruel, but Paradox won't let him, ever. While at the beginning of the "Groundhog Day" Loop he was an unrepentant monster, by the time we've seen him, he's been trapped for several hundred million years in his own Ironic Hell and wants to pull a Heel-Face Turn, but Paradox is forcing him to remain an Evil Overlord. Seeing him actually tell Twilight not to stop the No-Holds-Barred Beatdown the rest of the mane cast are giving him because he deserves it and making them promise not to do the same to Mad Tiara and Screwball (his own family he has left) makes him rather sympathetic.
"Nightmare World: Broken Mirror" does this with Nightmare Mirror in an Alternate Universe were she won. After a thousand years ending with her having managed to remove the concept of deceit from the world...she shuts down her defenses and lets the Princesses capture her without a fight because she won't lie, because she's the 'Cruelest of Truths', she can't hide from the fact she's a criminal who did horrible things to make her dream world a reality. Despite succeeding, her methods of obtaining it mean even she can't deny the evil she's done.
Alien Geometries: Discord's castle in the Dark World. It constantly shifts both exterior and interior, seemingly as much of its own will as of Discord's, and many of its rooms seem dedicated to psychologically breaking ponies for Discord's amusement. Oh, and for bonus points, one room is a void that leads to Ponythulu's domain.
Pandora's Realm also has them, being a giant nonsensical labyrinth.
All Just a Dream: Luna wakes up, gets told by Celestia her night out with Pip has gotten her painted as a molester by the tabloids, has an arguement with Celestia at a guardian party, kills and revives Pip as an immortal zombie, turns evil again, tries to murder her sister, only for Celestia to break out her ultimate weapon and fight back. Luna gets bisected by a spear and... wakes up in her chariot next to Pip. It's left unrevealed as to rather or not this was a vision of a possible future or simply a nightmare, either way, it teaches her a lesson she really needed to learn.
"Character Rerailment/There Are No Bad Seeds" is a subversion. Silver Spoon ends up having a nightmare where she experiences the events of "One Bad Apple" trapped in her own body as it acts out her actions in the episode. The subversion comes from the fact it's actually her being Mind Raped by the now Nightmare Diamond Tiara trying to convince her her only role in the world is to be her minion. Silver breaks the nightmare and drives Diamond off by showing her resolve to save her.
All of Them: Shining threatens to throw the book at Thunderchild and clarifies he means this. Given they're in a library at the time, it would rather sting...
Thunderchild: "Even the Roedinian literature? There are some big books there..."
All There in the Script: The audio adaptation refers to The Voice in the Dark World chapters as "the Nameless Passenger" for the sake of having something to refer to it as in the credits. Likewise, its Good Counterpart is referred to as "the Benevolent Interloper".
Always Chaotic Evil: Subverted. Despite Discord being purely evil, being born of Disharmony does not automatically make one evil. This is a major plot point in Fluttercruel's story arc. It's also revealed that Discord was simply one of a group of Draconequi, but seems to be the only truly evil one of the bunch. We see some of the others in "Generational Transitions" and some of them are downright nice. Even Destruction, a Mad Bomber who loves blowing things up, has some degree of empathy for the ponies. Discord was having the time of his life doing whatever he pleased in a universe that was going to be destroyed anyway.
Not to mention that in "AJ's Dream," Liarjack (or one version of her) was shown to wield the Element of Kindness.
Also subverted with Diamond Dogs. The original trio actually end up entering a business venture with Rarity and Shining Armor reveals there are even some very loyal ones in the Guard. Completely subverted in Dark World were they were hyper evolved by contact with the Heart of Ponyland and became monks.
Also subverted with the Changelings, as some, such as Moth realized what they were doing was wrong. The two Changeling brothers who were sent to kill Trixie also had a Heel Realization and faked Trixie's death when she didn't show, then proceeded to smuggle some innocent ponies out of the castle in the chaos. It's later revealed that Weaver, Diver, and Bombardier are also heroic Changelings.
Amazingly Embarrassing Parents: Twilight and Shining Armor's, at least their mother. For one thing, she published a book...about a Harem ComedyIn Space. While Cadence and her hoofmaidens apparently enjoyed it enough that they all read it, Shining and Twilight are both humiliated by its mention (Shining more so for accidentally giving her the idea to put it in space).
Dark World!Rarity is described as this after her Heel-Face Turn and getting a bath, due to hauling around Tom and tons of other rocks around for centuries in addition to being one of Discord's Co-Dragons making her physically powerful. While Spike doesn't care about her appearance, it's definitely a plus.
Apparently, Discord created an island of Amazonian mares...who all look like Shady.
And I Must Scream: Discord shares the same fate as his canon self. Ironically, being Taken for Granite is normally a subversion in this universe. It is actually surprisingly pleasant for the average person, you just peacefully contemplate your place in the universe, mentally compose poetry, and generally remain in a peaceful, zen-like state and aren't even traumatized when you're freed. It's only this for Discord because he can't stand being sane and peaceful, so it's torture for him.
A voluntary case in Nightmare Whisper, who reveals that the pain and suffering that she bears has already killed her twice, but she keeps using her power to bring herself back to life so she may continue to bear it.
Celestia's description of what she would have done to Fluttershy if she had inadvertently killed all of the unborn foals of Equestria. "I would have torn out your soul... and sealed you away for a lifetime per every life you had ended. In the sun, your soul five thousand miles below the surface. Able to feel everything."
You know how Dinky was turned into a muffin in Epilogue? Dark World 14 reveals that she was conscious the entire thousand years!
Dark World!Discord was on the receiving end of one by Nightmare Paradox. Spent what amounts to several hundred million years trapped in a "Groundhog Day" Loop that always ends with his and Fluttercruel's deaths. He considers being Dragged Off to Hell and killed several billion times by his family as punishment for his crimes relaxing compared to it.
To put this in perspective, according to a Loose CanonRecursive Fanfiction, the Valeyard considers his fate less horrific than what Paradox did to Discord. The Valeyard is saying this while in Hell.
Sweetheart's little sister Cream ended up suffering this in Sweetheart's Gaiden story. The explosion ended up 'locking her in', meaning her body was paralyzed to the point she couldn't even speak, but she was completely aware and conscious of everything. Including being dragged off and torn apart by mutants created by the explosion, taking this trope literally in that she literally couldn't scream. Worse in that because of her condition, they may simply went straight to eating her alive.
Another potential candidate for this trope is Nightmare Mirror in the Dark World. Her very status as the Cruelest of Truths means that she is fully aware of all of the flaws in the Dark World, and unlike the other Nightmares, she knows that the ponies are all living beings, no matter how much Nightmare Paradox insists that they're all just unimportant NPCs who aren't even real. This means that assuming she gets purified by the Elements of Harmony, she is going to be hit extra hard by Heroic BSOD combined with My God, What Have I Done?, and will probably become The Atoner even more then the other Nightmares. It's eventually revealed that Mirror is completely aware of just how horrific the Nightmares' actions are and they're earning an eternity in Hell for it, and even the thought that the end result will prove The Extremist Was Right isn't enough to make her stop hating herself for it.
Makarov's 'Alicorn' Cyborgs. The moment that Shining frees the first one, Yablokovodka, she breaks down sobbing and Mother Deer implies she was completely aware the entire time and Shining killing her had been a Mercy Kill.
When Makarov Ret Gones the Changelings with his Reality Warper powers, the story cuts to Ponyville where Moth, a benign Changeling living with Lyra and Bon Bon, is left invisible and incapable of interacting with them, but capable of hearing them talk about her 'death' while she's helpless to do anything about it. The scary part is Makarov does this casually.
When Shining breaks Makarov's antler off and later when the Lights begin leaking out, he starts hearing the voices of Makarov's victims begging him to kill Makarov. The implication is everyone that Makarov has consumed is suffering one of these!
Silver Spoon during "Character Rerailment". Nightmare Diamond traps her in a nightmare where she must watch her body act out the events of "One Bad Apple", only able to act when she wants to do or say something the canon Silver did. She spends most of it watching her body laugh as the Crusaders are tormented by Babs Seed. Thankfully, she finally escapes in the end.
Chrysalis mind control seems to be this for certain ponies. Twilight and Applejack both show signs of being aware of what she's forcing them to do while Moon Dancer's mind control broke down and almost destroyed her mind while she tried to help stop herself from helping her to no avail. Applejack's response to being asked what being brainwashed was like was to refuse to talk about it due to how horrible it was. However, Sweetie Belle and Spike haven't shown signs of this, with Sweetie almost seeming happy to do Chrysalis' bidding. It's hard to say which is worse. This is worse for Applejack because Chrysalis spent three days actively torturing her before she was freed.
Animesque: The audio-adaptations have recently been taking a step in this direction, complete with an official opening theme that's actually shortened for each installment and title cards!
Anti-Hero: Trixie after her Heel-Face Turn. She's undoubtly on the good side, but she's still got a lot of issues to work around and is willing to use methods that aren't exactly heroic to get the job done.
Anti-Villain: Princess Gaia is a Type III, as she genuinely believed she was doing the right thing and never killed anypony, but was also insane and tried to force her vision of the world on the world.
The Chaos Six in Dark World are a Type II, with the exception of Fluttercruel or so it seems. They've been emotionally broken and brainwashed by Discord, and don't want to be evil. The moment they're able to break free, they do.
Nightmare could technically be a Type II with aspects of Type III. By nature, Nightmares are insane and generally Woobie, Destroyer of Worlds with good intentions.
General Hercules Beetle is a Type IV. He lacks the Changelings' Fantastic Racism and actually respects the ponies. He sees them as entirely in the right to fight back against the Changelings and generally seems like a good person. However, he took oaths to both Cocoon and Chrysalis and refuses to break it. So his being a villain seems to more be due to Undying Loyalty than genuinely being evil.
Anyone Can Die: Zigzagged in the Shining Armor Arc. Once the final battle Makarov begins, characters both major and minor start dropping like flies. However, due to the nature of Makarov's defeat, they're all resurrected once he's dead.
Razzaroo from the G3 universe wrote one as her final act, being allowed to finish by Pandemonium due to it being her final work. In The Stinger, Twilight gets her hooves on it thanks to the Interviewer.
Bon Bon the First's diary, which details the aftermath of the destruction of civilization Destruction triggered to prevent the G3 universe from being created.
Apologetic Attacker: We don't see it, since it's happening in Trixie's head, but Princess Starflower apologizes before smacking Trixie on the head with a mallet to snap her out of Princess Gaia's Lotus-Eater Machine.
Princess Gaia/Nightmare Whisper herself is also one.
Appease the Volcano God: Mentioned in Bright Eyes' chapter in a Call Back to My Little Pony Tales. Back in the present, Twilight and Pinkie ask Luna if there actually are volcano gods. She replies that while there are deities who qualify (some of which she's related to), none of them require pony sacrifices, that was a Lava Demon thing.
Almost all the stories end with the pony in question accepting her new position, declaring "I'm free." In the Discorded Series, this is normally a bad thing, but in the Reharmonized Series, it's a good one.
There's an arc SONG in the form of the three "So Many Wonders" reprises. The first is about Fluttercruel's happiness over being free from Fluttershy and able to see the world, second is a Villain Song by Princess Gaia used to hypnotise ponies into her vision of the world, and the final is a Triumphant Reprise at the finale of the arc, Fluttershy and Fluttercruel singing together about how their worldview has changed for the better.
"Dying is easy, living is hard" for the entire series, but especially the Dark World. While in the main series it deals with overcoming what Discord did to them, in the Dark World it's about living with what you've done and the world you live in.
"Forgiveness is not earned, it's given" for the Dark World. In addition to the above theme, Forgiveness is an overarching theme, both being able to give it and being able to accept it.
"Sweet Music" for Melody's 7 Dreams/Nightmares Gaiden story, both the song and the words. First it's part of Melody's fame, then it is the name of her daughter but the song itself is something that must be kept quiet or it'll get the family killed (Melody was made The Scapegoat for the disaster). In the end the song and the words come to represent Melody's legacy, which lives on her in descendants Rarity and Sweetie Belle.
"You've got a lot to learn about ponies" has cropped up in the Wedding Arc, usually when one of the heroes is talking to a Changeling.
Armor Is Useless: Subverted. The Shining Armor Arc has armor which, while not COMPLETELY invulnerable, has protected its wearer from more serious injury. It's just Shining Armor's shield spells are more effective so they're more frequently used.
Subverted even more so later on when the special armor he obtains as a gift from Pandora saves him from a sniper round to the chest and later stops Gilda from being killed instantly by Makarov, allowing her to perform a Last Breath Bullet that destroys the Iron Curtain.
The Changeling's natural armor is also a subversion. It protects them from bladed weapons, though blunt weapons do hurt them more successfully.
Rarity: Dash…we all have a choice…Ours is to save the world…I've chosen to want you back as my friend…But what do YOU want to do?
Dark World!Rainbow Dash later returns the favor after ripping out her own Element to snap Rarity out of her own self-delusion. Also a Call Back to Rarity trying to forcibly take it when Rainbow was suicidal.
Rainbow Dash:Not so hot when you have to do it the dirty and ugly way is it?
Twilight: What does hurting a monster who's already dying and no longer a threat to anything DO? Payback? Retribution?
Dark World!Discord manages to do this to himself by proxy of asking the question to Twilight and hearing her answer, making him realize there's one choice he can make to stop Paradox's "Groundhog Day" Loop plan.
Discord: ...Twilight...what would you say if I said I never had a choice?
Twilight: ...I'd say you were wrong. You always have a choice.
The Interviewer's get one on General Hercules when he's describing his desire that Chrysalis had taken Sweetie Belle's Last-Second Chance. It doesn't cause him to have a Heel-Face Turn, but it seems to shake him up a bit:
The Breezies were taken directly to Heaven by Abbatissa, the Alicorn of Prayer, as opposed to being remade or erased, with the exception of Daisyslow and Zipzee, who stayed with Rainbow Dash, becoming Derpy and Fluttershy respectfully. It seems be partly because of their selfless personalities and partly because Zipzee managed to perform a miracle to break Discord's spell on the Breezies. They also got to take Breezie Blossom with them due to Divine Intervention literally answering Zipzee and Daisyslow's prayers, though Abbatissa makes it clear it's only because of very unique circumstances that that was possible.
Fluttercruel fights her way back fromThe Void to confront Nightmare Whisper after being doomed to non-sentience, because she truly cares for Fluttershy as a parent and a friend and doesn't want her last thought to be that she led Fluttershy to evil.
Trixie to some degree, as all the things she'd not felt guilty about now cause her a great deal of it.
Dark World!Applejack after her Heel-Face Turn. While Twilight has this too, Applejack's is more pronounced as she wants to earn her place in Pony Heaven next to her sister.
ALL of the Dark World Mane Six count after each has had their respective Heel-Face Turn really.
Dark World!Discord, due to having long since had a Heel Realization during the "Groundhog Day" Loop and only being evil because Nightmare Paradox is forcing him to. When Rancor throws a wrench in her works, Discord Out Gambit her and gets Twilight to see his memories to give them a chance to stop her. When we next see him in the afterlife, Discord has already sent apology letters to Pinkie Pie and Fluttershy and is willingly allowing his family to punish him.
Audio Adaptation: A very large fanproject presently in the works is making one of these. Yes, the entire fanfic from start to finish... already available in two languages note English and German, nontheless.
Author Appeal: Kendell2, the co-author of the Shining Armor arc, is a huge fan of Super Sentai and Kamen Rider. Once he became the co-author of said arc, numerous references to the two series started cropping up in the arc.
Every military leader in Shining Armor's story, including Shining himself, Master Chief Spartan, and General-Admiral Makarov, is more than capable of keeping a lot of flank.
Awful Truth: Applejack willingly steps up to see this by looking into the Truth in order to fully understand the thing that Discord used to break her. She learns a lot of harsh truths, but ultimately uses them to help everypony. It also causes her to become a Living Lie Detector as a result.
The Corrupted Six in the Dark World timeline are this to varying degrees. While Angry Pie and Fluttercruel are your typical "bloodthirsty psycopaths who get off on murder and torture" insane, the others have more subdued forms on insanity. Twilight Tragedy is chronically depressed and down, physically incapable of seeing joy or hope in anythinguntil her meeting with Apple Pie, Liarjack is physically incapable of telling any truth at all until her reunion with Applebloom, and Greedity is a deranged Attention Whore who literally lusts over a pile of rocks. The only one who isn't insane in some way is Traitor Dash, but that doesn't stop Discord from tormenting her and forcing her to be his lapdog.
In Reharmonization, Discord made Archer arrow-crazy and both Silver Spoon's father and Golden Harvest literally Ax-Crazy.
General Admiral Makarov, the Big Bad of Shining Armor's Arc. 'Send a small army to try and kill them' is his default reaction to you not knowing his name.
Queen Chrysalis, but in a more subdued way than the others. She's a mass murdering sociopath with a sadistic streak a mile long, but for the most part her psychotic nature is kept subtext rather than in the forefront like with Discord and Makarov. In a way it makes her more frightening, as she feels more off than over the top.
Back from the Dead: Apparently happened to Tirek offscreen over 1000 years ago. The Rainbow Of Darkness regenerated and brought him back to life with it, after which he challenged Luna for the title of ruler of the night. While we don't learn the details, Luna won and claimed his chariot as her prize.
One of the Recursive Fanfictions contains a more back from the nonexistence example. After being RetGoned from the Pony POV universe by Entropy for refusing to become a Nightmare, Neo Stream is "reborn" in...the Garry's Mod verse!
It should be noted this is normally a defied trope; Mortis apparently specifically has a rule against this happening and is said to have good reason for it. Celestia and Luna's second life on Earth is specifically said to be cheating and something that normally wouldn't happen. How Tirek did it is presently unknown.
Mortis permits Queen Libra to do this with all those who died as a result of Discord's evil in Dark World who desire to come back (those who die of old age or unrelated causes couldn't). Among them are Granny Smith, Scootaloo, Gilda, Magica, Poison Apple, Tom, and Sparkler. Sadly Applebloom and Sweetie Belle died of old age, and couldn't be resurrected, while Pinkie Pie died of Rapid Aging and Fluttershy has those that still need her.
Dima, Gilda, and the rest of Makarov's victims all are restored when he's destroyed. Justified as Makarov's erased from history, repairing all the damage he'd caused, including those who's lives he ended.
Backup from Otherworld: The Dark World Arc has the loved ones of the mane six return from beyond the grave to help guide the mane six back from their corruption. Cadence (possibly Trixie, it's kind of unclear) help Twilight, Apple Bloom helps Applejack, Sweetie Belle helps Rarity, and Scootaloo helps Rainbow Dash. Though out of all of them, Sweetie Belle is the only one to physically manifest, in the form of one of Rarity's golemns. Later on, Roseluck, a former companion of the Doctor, returns during the fight with the Valeyard using the same method as Sweetie Belle and actually physically joins in the fight (though her physical form is destroyed) and guides Rarity to the Valeyard's regeneration template, as well as entering his body and helping restrain him.
Dark World!Fluttershy returns to hold back Cruelty's spirit after her second body's destroyed, allowing the heroes to use the Elements to banish her from the mortal plain. Pinkie Pie also does this, since she died during the battle, but her spirit blocks Cruelty from possessing Twilight, setting up Fluttershy's.
During the Final Battle with Nightmare Paradox, Discord distracts the Nightmare to give Twilight time to power up the final spell to defeat her once and for all. By calling her on Anarchy's cellphone from the afterlife. And Trolling her until she's so enraged she forgets she's in the middle of a battle.
Rota Fortuna: You should leave all the same. Or would you rather I 'kick your flanks', as she so eloquently put it, again?
Subverted with Shining Armor in 17.2. Shining tries to make one after escaping Makarov's clutches, but it falls flat when the Griffins he's talking to have no idea what he's talking about. Double Subverted when Makarov's flagship blows up in the distance and confirms his boast.
Sandgriff: We thought you were being held in that fortress.
Shining Armor: Makarov threatened my little sister, so I blew it up.
Sandgriff: ...The completely intact fortress to the south?
Shining Armor: Uh, sorry, it was a big ship, I forgot it was a ship.
Natasha: Eh, easy mistake, it was pretty much a flying fortress.
Shining Armor: It's still bad flank I blew it up, right?
Frost: Blew what up?
He does get a good one the following chapter, however, after rescuing the rest of Misfit Actual.
Chrysalis gives an epic one to the Unicorn Interviewer in the Wedding Arc after the latter is freed from her control:
"I knew fate would contort and twist back upon itself before ever allowing me to claim my hard earned victory. But tell fate this, Half-Light Dusk. If the game will cheat before letting me win, I simply have to change the rules. I WILL stand on equal footing with her. I will no longer be her or anyling else's slave. Not her, not Cocoon's, not my flesh, and most certainly not that mad creature that thinks himself king of everything. He's next on my list. So tell me I am doomed, tell me I have no chance of winning, that I never had any chance of winning, I've heard it many times before, and I have proven them all wrong! I always grant those who look down on me their just reward. Send me to Hell and I SWEAR by every changeling that has ever lived, I will devour it from the inside out like a cancer! Tell me an infinite number of others have made the same boast and failed and were but toys for Havoc in the end, I will be the one to make that boast reality! Lock the gates of Heaven and I will break through them! Dump me in Oblivion and I will claw my own way out! I've come too far, I have struggled for too long, to see all I have made with literal sweat, blood, and tears, to crumble to dust now. I refuse to lose!"
Badass Pacifist: Fluttershy, naturally, counts as one until she becomes Nightmare Whisper. She manages to subdue Fluttercruel in a completely nonviolent fashion.
Also shows it during the Wedding where she weaponizes dodging.
Mother Deer, the Mother Goddess of the Deer. She managed to convince several Hooviets pull a genuine Mook-Face Turn just by talking to them.
The Brotherhood of the Scorpion. While a group of pacifists who have frightening tastes, they still managed to out coup the Hooviets and take control Maasailand.
Badass Santa: In the Dark World timeline, the Equestrian Santa Claus breaks into Discord's fortress yearly to read aloud his naughty list and distribute lumps of coal.
"Epilogue" shows one where Discord won and rules the world. It's not pretty.
It turns out there's a Bad Futurefor the Bad Future in the futures Nightmare Paradox comes from where Twilight goes Nightmare and erases Dark World to continue the "Groundhog Day" Loop she trapped Discord in. From what we see, the set up for some of those is worse than the Dark World in that typically either some or all the mane cast minus Twilight dies fighting Discord or there's planet wide destruction and death in some fashion.
We see another one in Luna's second sidestory. Luna turns evil again, kills and revives Pip as an immortal undead, and attempts to kill Celestia, killing a number of innocent ponies in the process, only for Celestia to ultimately kill her to protect Equestria. Turns out it was All Just a Dream, or at least a vision of a possible future.
To some degree the present is this, particularly for the Deer. The Shadow of Chernobull was released from Pandora's Box and became General-Admiral Makarov, who altered history so that the Hooviet Empire never collapsed, resulting in not only a horrific military dictatorship remaining in power for 20 years longer than it should have, but all the atrocities that Makarov and the Hooviets have caused since. The goal of the Rebels and Shining is to lure the Wolf to Makarov so it can erase him from existence and Set Right What Once Went Wrong.
Cadence receives a vision of what will happen if Chrysalis wins, and it certainly counts. Chrysalis activated a rune that rips the emotions out of every creature in Equestria and absorbs it, becoming a being strong enough to overpower Discord and conquer the world, reducing all other sapient beings to slaves, turning Sweetie Belle into The Dragon, and remaking the Changelings into her own twisted version of perfection. Cadence is naturally horrified by this.
Badly Battered Babysitter: The two Night Guards Luna leaves in charge of the four Day Guard Pegasi turned foals end up this way.
Baleful Polymorph: Discord did this to a great many ponies. During her adventure in Canterlot, Applebloom somehow ended up being unwillingly transformed into a Sea Pony. Even Applejack isn't sure how that even happened.
This is Kabuto's fate during the Wedding Arc: his mutations meltdown and turn him into an Earth Pony.
Bargain with Heaven: Joining the Royal Guard seems to work this way. It involves being infused with a bit of the Princesses power (each do half) with a bit of transformation involved, more for Luna's than Celestia. However, the contract is very thorough about this (at least in Luna's case, it's in big bold letters across two pages in size 40 font, complete with before and after pictures) and applicants know exactly what they're getting into.
Batman Gambit: How Celestia convinces Trixie to stop fighting her awakening Element Of Magic.
Battle in the Center of the Mind: Pinkie Pie has one against an evil fractured piece of her personality called Angry Pie caused by Discord's corruption. The final battle with Loneliness takes place in the center of Trixie's mind, which has been rendered a Crapsack World by Loneliness' taint.
Be All My Sins Remembered: Despite the fact there are a great many ponies who love her for what she did, Fluttershy outright says in her speech she'll accept rather whether ponies choose to love her for the good she did or hate her for the bad.
Fluttershy: I didn't do everything right, I did bad things I don't know if I'll ever stop regretting. Some ponies won't ever forgive me for those things and maybe they're right to. I'm sorry for those things, but I wanted to help ponies, and it looks like I did. And I'm happy I was able to. And for everyone hearing this, if you'll take me back for what I accomplished, I'll accept that. If you won't take me back for what I did, I'll accept that too. I make no excuses, what I did I did and I was being a foal.
Being Evil Sucks: In the Epilogue/Dark World timeline, Liarjack, Traitor Dash, and Twilight Tragedy all hate what they've become, but Liarjack and Traitor Dash can do nothing about it, while Tragedy has effectively given up all hope and feels her service to Discord is all she has left. Averted with Angry Pie and Fluttercruel, who not only embrace their newfound evil, but relish in it.
The Nightmare Manacle and Mirror in Paradox's group Psycho Rangers are the same way; Manacle still loathes herself possibly worse than Traitor Dash did and Mirror? She's completely aware of how horrific the Nightmares' actions are and knows they're earning a spot in Hell for it. The only thing she has left is the idea The Extremist Was Right and their world in the end will be worth it.
Derpy: You pill hate yourself, won't blue, Rainbow Dash?
Don't hurt one of the Crusaders, the others will Get Dangerous and do anything to protect them.
Chrysalis can't stand being underestimated.
Better Than New: Happens to Pinkie Pie during her week long slumber after she finally crashes from going a week without sleep. She wakes up able to think clearly and say things so profound (though still in character) that even Twilight is incapable of arguing her points. This happened because during that time she performed a Split Personality Merge.
Shining Armor and Princess Cadence. Despite being very nice Reasonable Authority Figures who would very much prefer a peaceful resolution to any conflict, do not harm innocents around either of them. General-Admiral Makarov found this out the hard way with Cadence when she powered up using the bonds of Misfit Actual to stop him from slaughtering a village and curbstomped him. Shining? He crushed a Diamond Dog to death when it killed his uncle in front of him and when Makarov tried to repeat it with Twilight, smashed Makarov's Doomsday Device and almost crushed him to death.
Ponykind (or at least Equestria) in general seems to be this. They can basically be described as a race of pacifists who want to befriend the entire world and consider the idea of killing as something that, at best, is a last resort. Despite this, when threatened by an evil force, they're no less capable of kicking flank than anycreature else, and have consistently held their own against threats from monsters like Tirek and Lavan to military Empires like the Hooviets and the Changelings. They just prefer to exhaust the possibilities for a peaceful resolution before kicking your flank and are likely to offer a hoof of friendship after doing so..
Natasha, the sniper among the Rebel Deer, has a modified sniper rifle that shoots 14mm rounds (which are Heavy Machine Gun rounds). It's named Sasha.
Makarov has a massive horncannon of his own. It's gold plated. It gets progressively more gaudy as the story progresses.
Big Bad: Loneliness for the overarching plot with fixing Trixie. She's an entity that was keeping Trixie from being saved after Discord broke her. When Twilight enters Trixie's mind to free her, she ends up trying to kill her repeatedly to keep Trixie under her clutches until she's finally destroyed by Trixie rejecting her. Unfortunately, Discord's Mind Rape on Diamond Tiara causes her to free him and let him take over as the main villain.
However, before his arc happens, Fluttershy's Superpowered Evil Side Princess Gaia/Nightmare Whisper serves as the Big Bad for her self titled story arc.
"Origins", being a prequel, naturally has Discord as the Big Bad.
As of "The Real Hoof Blues", it would appear The Voice is the Big Bad of which he spoke. She even makes an attempt to corrupt Twilight into a She Who Fights MonstersNightmare. It is later revealed that she's a version of Twilight who already became what she tried to make Twilight into and Twilight's potential future self, Nightmare Eclipse/Paradox.
Then, Discord is stabbed In the Back by Rancor, who steals Destruction's power back and leaves him mortally wounded. He gives his power and the power of Havoc's Avatar to Fluttercruel. She then becomes the Dragon Ascendant and attacks the heroes of her own free will with the motivation of using the Elements of Chaos to save her father's life.
Also from the Shining Armor Arc, The Master is this from Minuette's perspective, having spent the entire story trying to influence her to open her fob watch and become him again and since The Reveal, actively trying to tempt her into doing so every chance he gets. Not a Big Bad Ensemble in that, at present, Shining Armor is unaware of his existence and he's not threatening Shining deirectly like Makarov and the Wolf have. Like the Wolf, he's defeated in the Grand Finale of the Arc.
Sharp Spear in the last leg of Melody's '7 Dreams/Nightmares' Chapter. Even if he only appears in person for one scene, he's still more or less responsible for nearly everything bad that happens to Melody's family after her daughter's birth due to his Fantastic Racismincluding basically kidnapping her daughter and unlike the villains in Patch's tale, is the only antagonistic force in the storyline.
D___t's Shadow of Existence in Bright Eyes' Nightmares section. He tries to devour Zipzee at the end of G3 by forcing her over the Despair Event Horizon so he could take her infant Concept and become real again. After that failed, he spent the entirety of the Nightmares section stalking her, trying to increase her feelings of depression and fear to do the same before finally trying to take her Concept by force to become real, forcing her to destroy him completely.
Dark World!Rainbow Dash does this twice during the battle with Odyne!Cruelty, first by shattering her Ultimate Stare and saving the group, then by plowing through several walls and delivering a Sonic Rainboom tackle to Cruelty's back to save Rarity.
Does so again, accompanied by the Princesses (who she flew up into space to recharge directly from the sun and moon), during the Final Battle, arriving in time to save the group from Paradox and her Psycho Rangers.
In Bright Eye's Gaiden Story, Logan saves Lancer and Bright Eyes from an Ahool using the Yellow Shard of the Rainbow of Light to calm it down before it can kill Lancer.
Later its revealed that some kind of deer deity saved Bright Eyes from some coyotes when she was a filly, which caused her to develop her environmentalist views.
Twinkle Shine and company due this at the end of Chapter 10 of the Wedding Arc, after Chrysalis has managed to barely beat Celestia and repel Luna's counterattack via Shining's shield supercharged by her magic.
Trixie comes to Cadence's aid during her fight with a Brainwashed and Crazy Twilight Sparkle, throwing a wrench in Chrysalis' plans.
Trixie tends to make these whenever she physically can.Comically parodied when her doing so during the wedding arc causes a misunderstanding with her friends.
The Big Damn Kiss: Garnet gives on to Running Gag after he uses his language skills to trick some Hooviet mercenaries into going the wrong direction, allowing Misfit and the Doctor to escape without a fight. To add to the awesomeness, Cadence promotes him on the spot.
Bigger Bad: Discord. He's already been put back in his can before the Reharmonizing series begins, but the aftermath of his actions have had deep and lasting effects on everypony.He eventually breaks free and becomes the Big Bad proper for the finale.
In addition it's revealed Discord was responsible for King Sombra, having gotten one of his cousins to orchestrate his creation due to his own hatred of the Crystal Empire. However, by the time Sombra's creation was complete, Discord had long been defeated and Sombra was primarily a self contained threat.
The Nameless Passenger/Nightmare Eclipse/Paradox turns out to be this for the Dark World, as while Discord is the primary villain, it's only because of her actions he's allowed (and to some degree forced) to remain the Big Bad, as otherwise he'd have been defeated or turned goodcycles ago.
Father Deer presumably for the Shining Armor Arc, given he's Makarov's boss. Subverted in that Makarov is more than he appears and the Father Deer is simply a figurehead.
In a way Makarov is the Bigger Bad of the Wedding, his Rewriting Reality to kill off the Changelings being what allowed Chrysalis to become a much bigger threat, long after his demise.
In the alternate Story Of The Blanks timeline where the bone fiends got Apple Bloom, Applejack "proceeded to tear Sunnytown to its foundations and [buck] the head off of any zombie pony that got in her way."
Loneliness' final form is a clone of the Great and Powerful Trixie.
Queen Cocoon pulls this after Chrysalis defeats her One-Winged Angel form, transferring her soul to a fresh clone and emerging as what amounts to a clone of Chrysalis (minus her 'deviant' eyes).
Ironically, Chrysalis herself ends up doing the exact same thing, her final form being an Evil Twin of Cadence (with some minor differences) named Cadenza due to being completed by the Elements of Harmony on account of her being the original Cadenza's Shadow of Existance.
The Dark World Series eventually ended this way. The world is saved, the Chaos Six have all been redeemed, Spike and Rarity are Happily Married, the ecological damage from Discord is fixed, and Queen Libra is permitted to bring back anyone who died from Discord's evil if they desire it. However, Fluttershy, Pinkie Pie, Applebloom, and Sweetie Belle were Killed Off for Real, Twilight and Rarity have become Alicorns to make it possible, meaning they've given up any chance of ever being reunited with their loved one in Pony Heaven, and Twilight has to leave to perform her duty as Concept of Magic and Happy Endings.
The Nightmare Granfalloon timeline. Yes, half the mane cast are dead, and Granfalloon's rampage caused a lot of pain, but Golden Tiara is sane again and reunited with her family, meaning that Diamond Tiara won't let Discord out of his prison again. On top of that, Word of God confirmed that Fluttershy in this timeline never becomes Nightmare Whisper.
Depending on how you look at it, "Generational Transitions" ends like this. Yeah, the G3 world ended, but the universe was saved from dying for good, meaning a new one will take its place. Plus, even though Minty died Pinkie saved her from being deleted, allowing her to live on as part of Twilight Sparkle, and was saved from deletion herself.
Havoc: I Heard Your Rant About Villains Not Playing By The Rules 325,285,347 Times, Your Claim About Perfection 186,032 times, Your Speech About Life 432,874,222 times, Your Declaration Of Controlling The Universe 987,873,365,321 Times But Your Final Speech Was Something New For Once.
Nightmare Eclipse's claim she chose her name for eclipsing Celestia and Luna and exceeding them is considered this by the Dark World!Mane Cast. She also claims to be above all the other Gods and outright states she's going to destroy the Goddess of Fate.
Queen Chrysalis' Villain Song in chapter 16 of the Wedding Arc starts with one of these:
Queen Chrysalis: I am mightier than the Sun,/More cunning than the Chaos./More beautiful than Harmony,/I put her face to shame" .
Blue and Orange Morality: The Draconequi have a form of this. Their role in creation makes it impossible for them to have the same moral framework as Alicorns and ponies, but they still have a form of love that allows them compassion and they do each have some degree of empathy and compassion, without which they'd be...well, Discord. They also enjoy chaos because they're born from it. But even by their morality, Discord's is black and doesn't so much enjoy causing chaos as the suffering he inflicts while doing so.
Also applies to Dragons (minus Spike) and Diamond Dogs. Both of which are stated to be instinctively greedy beings and thus their form of morality revolves around it, but neither are not completely selfish or immoral. They consider their loved ones possessions, and thus extend their protectiveness of their possessions to them. Diamond Dogs also are willing to die for their pack (including adopted members).
This is the entire reason that the world is scared to death of Maasailand. The country simply have somewhat inverted perceptions of what other cultures think of as symbols of good and evil. So what they think makes them look like a peaceful, beautiful place to live makes them look like Mordor to the rest of the world.
Lots and lots of this are involved in Discord's games.
Garnet, being medic with knowledge of biology, realizes this trope applies to Kabuto's additional limbs implanted into his back. The thought of how he got them (on top of the poor Changelings he killed perfecting it) literally makes her ill. What we've seen of Kabuto's experiments imply this is abundant in them.
Book Ends: The first glimpse of hope we see for the Dark World is Apple Pie saying "Hey, even in the darkest of times you hav'ta find something to laugh about!" She and Twilight say it again as their goodbye to one another as Twilight leaves Dark World after they've finally saved it.
Applejack: It involved Applebloom spookin' every Pegasus in armor around, a royal fountain, Applebloom needin' to redefine her meanin' of 'public bath' . . . and Ah think the ghost of a Hippocampus and a lost family locket but Ah kinda ain't sure 'bout them details.
Discord: "Oh, but you all LOVED it when Princess Gaia did it! Don't worry, Shadows-Who-Watch, I'm sure you'll be delighted to see me one again doing to all Equestria what I've done to Diamond Tiara! Isn't that right, my little pony?"
Breather Episode: The first half of the Penultimate episode comes right after the climatic, and terrifying, battle with Loneliness and Fluttershy going all Nightmare Moon, but is just, for all intent and purposes, the cast just getting to know the "One and Only Trixie".
Also, New Game Plus. In between the first part of Mind Games, which is a tense 3 part series about Onyx Tiara healing while Diamond Tiara seeks to restore Discord, and the rest of the mind games which will arc into the finale arc, we have a brief interlude letting the author link the episodes not yet covered into the main story. There are certainly serious moments, but the overall tone is MUCH Lighter in comparison.
"Different From Everypony Else" is set immediately after "New Game Plus", but was published between the last two installments of Mind Games. It has its dark moments, but is ultimately very heartwarming, and even the dark moments don't compare to the content of Mind Games.
"ecnarbmemeR-Remembrance", a rather normal, lighthearted episode following Shining Armor was published right after the Darkest Hour of the Dark World Arc. While there are some creepy aspects, it's pretty much just a relaxing little chapter.
"Family Reunion" is about as lighthearted as it gets in the Dark World arc: before meeting the Apple/Pie family to recruit Apple Pie as the new Element of Laughter, Twilight and the gang decide to make themselves look more presentable by taking a bath; Hilarity Ensues as they try to bathe Rarigreed, the filthiest of the gang after spending a thousand years wallowing in rocks and dirt. Even their meeting with the family that follows goes over fairly smoothly (that is, as smoothly as things can get after some of the family members greet them with a few cautionary explosives).
"Retcon-Struction Blues" is sandwiched between two Dark World Chapters, one being the beginning of an all out brawl between Discord's remaining minions and the heroes, and the other being the continuation of that battle and a major Wham Episode. The chapter itself is about Twilight reconciling with the CMC from the Smartypants Incident.
Shining Armor Part 11 is a short, uncomplicated story about the trip to, and the group enjoying their first day in, the zebra nation Zamura. This comes right after all the drama Shining went through in Columbia, and is posted right after the Dark World Mane Cast confront Nightmare Eclipse/Paradox.
"A Day at the Circus" is simply the mane six and the CMC enjoying a day at the circus. While it's a Loose CanonRecursive Fanfiction, the author fully intended it to be one of these for everyone, from himself and Alexwarlorn and the audience to the characters themselves.
Wedding 19 is simply the mane six reconciling and recuperating after rescuing Twilight and Spike.
Brick Joke: In Shining Armor's story; in part 1, during Blueblood's Verbal Backpedaling (after insulting Twilight in front of Shining), he says he was actually thinking of a Twilight Sharkle, who he then accidentally says is a shark. In part 11, a Major Dawn Sharkle is briefly mentioned, and the unit she's in has a title that spells SHARC.
Earlier in the Columbia saga, it's mentioned the country has 'no singing zones' due to random musical numbers causing traffic jams. Later on, Cadence's hoofmaidens had their own crazy adventure ending with them being arrested for singing in a no singing zone. Also, in part 11, before arriving in Zebrafrica, Cadence reassures the group no such law exists in Zebrafrica.
Rainbow Dash is terrified of this happening with her if it becomes known that she abandoned the game in the maze to save Cloudsdale of her own free will.
Turns out, Spitfire had the same fear, after the repeated failures of the Wonderbolts to help in an actual emergency. She also shows concern what she tells Rainbow Dash about herself might do the same. She's wrong, and Rainbow tells her that she and the Wonderbolts are heroes, because their actions inspire others and, at the very least, they're still her heroes.
Kind of happens to Pandora when Strife tells her their brother D___t wasn't the good Draconequus she idolized and was instead a Well-Intentioned Extremist by Dragonequus standards.
Broke Your Arm Punching Out Cthulhu: Type two. Thistle Whistle rams Strife head on with all her power to save Sky Wishes...and shatters every bone in her entire body, killing her. Though she did save Sky Wishes' life and Strife even acknowledges her bravery for the act.
Brought Down to Normal: Dark World!Celestia and Dark World!Luna, due to their magic being drained during their imprisonment. While they can probably recharge, at present they're powerless until then. They recover later
Bullying a Dragon: As one commenter points out, the Hooviet-Dragon war occurred because the Hooviets did this literally, and the end result was the destruction of the entire southern half of their empire.
Call Back: More have been showing up as the Dark World storyline comes to a close, especially in Part 20. Spike's hoof wrestling skills first mentioned way back during Trixie's party are what keep him alive against Rancor. Fluttercruel's ultimate technique is the same as her mother's: The Stare.
Odyne!Cruelty uses a version of Strife's Devil Blades Serpents attack called Strife Tribute: Hell's Gate Hydra.
The Cameo: Lady Babylon, the Big Bad of Godzillawolf's tumblr Blog has made a few cameos. Godzillawolf returns the favor by occasionally having Havoc and Entropy cameo in his works, as the two are friends.
Death by Cameo: Both cameos involve Lady Babylon dying in some fashion, the first by being impaled by an alternate Trixie and the second being an Avatar of hers having been erased by the Blank Wolf when she tried to send it there. Godzillawolf has no problem with either and has even said the latter is canon to his blog.
Remember the Parasprites? They're what Discord turned at least some of the Flutterponies into!
Twilight is actually a fusion of the G1 Twilight Sparkle and Pinkie's best friend Minty, and is that way because Minty died right in front of Pinkie and had her spirit transferred into the G1 Twilight by Pinkie.
Mild example: turns out, Celestia secretly sent backup, in the form of a Black Ops SAS team, to shadow Twilight and her friends in case they couldn't defeat Nightmare Moon.
The entire setting has been subject to this, thanks to the fact Chrysalis has been infiltrating for decades, and the changelings for centuries before her, meaning that no character can be trusted any more, and the whole world has been handed the Idiot Ball to let them do it.
Shining Armor: It started cutting through my riot shield with a bucking CHAINSAW that popped out of its back! Who equips a cyborg diamond dog with a chainsaw?!
Chaos Is Evil: Subverted for the most part. While Discord, the Anthropomorphic Personification of Chaos, is evil, he's not inherently evil, and did not start out that way. The rest of his family, despite embodying Natures Fury and being chaotic, are actually important parts of keeping the universe running smoothly and all have at least some concern for life. Any threat they pose is simply them doing their jobs. Discord is the exception, as he decided It's All About Me and decided to take over Equestria and turn it into his own personal playground.
Also subverted with the Elements of Chaos. Despite Discord brainwashing the Dark World mane six to use them to act as his Co-Dragons, using them in such a way is their incomplete state. Their completed state comes from realizing both sides of the Element (good and bad), and once they do so, the Mane Six perform a Heel-Face Turn and become Phlebotinum Rebels.
Chekhov's Armory: Oh, so much this. The sheer number of seemingly insignificant characters, events, or even small bits of dialogue that end up becoming extremely important later could fill a page all on its own.
Applebloom's adventure in Sunny Town was first mentioned in Applejack's Reharmonizing as one of the things Applejack saw in the Truth. During the Princess Gaia Arc, the citizens of Sunny Town appear in Princess Gaia's castle as her servants.
We find out in "Black Pearl" that Celestia has an alias called Sunny Day. She shows up in this alas in "Playtime" to distract the foals heading to Princess Gaia's castle.
Earlier in Dark World, Twilight (in response to one of the Valeyard's attacks) immunized the group to near every poison she was able to. Odyne!Fluttercruel is composed of mostly poisonous animals, and this immunity serves as an advantage during their fight with her.
The Crusaders accidentally summoning a Fire Elemental once. During the Wedding, Applebloom does it intentionally to ssummon one to distract the Changelings and cover their escape after saving Spike. They somehow summoned a Water Elemental, but still.
Ruby, who is mentioned repeatedly when it comes to Sunny Town. During "Playtime", a mysterous song snaps Applejack out of it so she can see through Princess Gaia's illusion. It's later hinted by Applejack to have been Ruby.
The Interviewers, who seemed to just be a narrative device in the beginning, have gradually grown more and more important to the story, to the point of dropping hints to the characters to lead them in the right direction and giving Twilight Sparkle Razzaroo's Apocalyptic Log, something that isn't supposed to even exist in this timeline.
Tom's last shard saves Dark World! Rarity from being killed by Fluttercruel.
Earlier in Bright Eyes' Nightmare section, it's established Lancer trained Bright Eyes to use a sword as bonding and continues to do so to help her survive in the post apocalyptic world. This ultimately enables her to defeat Cruel Eyes/D___t's Shadow of Existence in a sword fight at the end.
Child by Rape: Given how disturbingly close to actual rape that Discord's Mind Rape is described, Fluttercruel counts, as she was born from Discord's Mind Rape of Fluttershy. As if Discord doing this to Fluttershy wasn't horrible enough without this mentle image.
Whats worse — this is confirmed as what actually happened, for all intents, literally, as of Chapter 93 : Love Hate Bedlam.
Clones Are People Too: Despite being a twisted copy of Fluttershy, Fluttershy believes Fluttercruel has a right to be her own pony and how she was "born" doesn't matter. Fluttershy has a talk along these lines with Fluttercruel after Fluttercruel nearly performs a Heroic Sacrifice to defeat Nightmare Whisper, pointing out that, even though she's a copy, Fluttercruel managed to earn a unique Cutie Mark. Celestia then proceeds to give Fluttercruel the ability to switch places with Fluttershy at will so she can live her own life. "Trixie's Last Hurdle" reveals that they even threw her a Cute-ceañera to celebrate earning her Cutie Mark.
Alright, so she's not a "clone" per se, but Fluttercruel sees herself as just a knockoff of the real Fluttershy, not truly alive and completely unable to be a unique individual simply because of how she was created. This causes her a great deal of heartache because she really wants to be.
Subverted after she realizes she's real, regardless of whether or not she's a copy. When as part of their 'punishment', Luna brings up the possibility that Fluttercruel is a severelyMind Raped Fluttershy and "Fluttershy" is the copy, they don't care, they're both real, why should it matter which one of them is the "original"?
Screwball is an even bigger one than Pinkie, though she actually is crazy.
Coitus Ensues: Inverted. Bright Eyes finally decides to have sex with Lancer for the first time after losing her memory. Not only does Bright Eyesrefuse to go in detail about it other than saying it happened, it's a plot point because it triggers her memories of their relationship together.
Cold-Blooded Torture: Nightmare Whisper's entire existence. Not only is she strapped with all manner of torture devices and in agonizing pain, she's enduring the suffering of all of Equestria the whole time. All of this is pretty much self inflicted.
After the battle with Nightmare Whisper, Fluttershy still holds onto the suffering, not wanting to release it back into the world (and she also feels she deserves it as punishment for her actions). Later Pinkie Pie helps Fluttershy bear it to ease her suffering.
Chrysalis enjoys doing a mental version to her brainwashed slaves. Poor Applejack was tortured for three days before finally being freed.
Confusion Fu: Very common, with Discord (naturally), Pinkie Pie, and Dark World!Applejack being prime users due to their powersets. Part of what makes Dark World!Derpy an effective combatant is she has an unpredictable flight pattern. Dark World!Twilight gradually learns to make good use of this and even suggests it as the best method of fighting Discord because he's not expecting chaos to be used against him. It'd actually be a shorter list to name characters who don't use this at some point.
Likewise, Twilight Sparkle is a literal fusion of G1 Twilight and G3 Minty.
The G3 ponies who were recycled into G4 versions of themselves usually resulted in this, except for the cases who got regular reincarnation instead.
Condescending Compassion: Trixie receives this from a dream version of Twilight brought on by what seems to be the embodiment of the Alicorn Amulet. She also later receives it from the real Twilight due to Chrysalis' brainwashing.
Conspiracy Theorist: Onyx Tiara believes that door handles and tooth brushes are tools of the unicorns and their gryphon co-conspirators to keep hard working Earth Ponies at a disadvantage. He's also convinced that Celestia's good nature is a "mask that hides the Tyrant beneath" that every negative event in Equestria's history can be traced back to her. That, or its a unicorn/pegasus plot.
Continuity Nod: It's mentioned in the Shining Armor Arc that Zebra, Deer, and Minotaurs can see visions of other worlds and access knowledge they otherwise couldn't in locations where nine leylines converge and that one of the locations where this happens is in the Everfree Forest. This is later mentioned in Bright Eyes' Gaiden Story as a possible reason for Zecora having dreams about her past lives Kimono and Ms. Hackney.
Cool Down Hug: Used by Pinkie Pie to calm down Rainbow Dash when she slips so far back into her self loathing she loses it.
Cool Pet: In addition to the canon ones, we finally see what Luna has for pets. What are they? Windigos! They provided the "special effects" for the Hearth's Warming Eve play.
Colour-Coded for Your Convenience: According to Moth, a Changeling's magic color is dependent on who they've pledged loyalty to. This was shown earlier with the Changelings having a different magic color under Cocoon than Chrysalis. This is later shown to be the case with Weaver, Diver, and Bombardier, who's magic matches Celestia.
Queen Chrysalis' origin story is a straighter example, to the point some readers have even called it 'Lovecraftian'.
Alexwarlorn seems to have a knack for turning villains' origins into these. A one shot chapter explaining how the Crystal Empire fits into this universe has this with King Sombra's origins. He's not actually a unicorn, but a Equinoid Abomination Discord got one of his cousins (which seem to include several Lovecraftian deities) to trick the crystal ponies into siphoning off their negative emotions, primarily fear, which was fed into the ground deep underneath the Empire. This eventually created King Sombra, who emerged and conquered the Empire, making Sombra literally the suppressed fears of an entire kingdom given shape. In addition, there's even creepy chanting in an alien tongue while Discord's unnamed cousin awakens his creation.
Cosmic Retcon: The Alicorns and Draconequi were originally in charge of this according to veryLoose Canon, but only if a universe was on the verge of entropy and needed a drastic overhaul if there was any hope of saving it. They retconed the G3 universe into the G4 universe because it was on the verge of dying if they didn't.
More like destroying the G3 universe and rebuilding it completely as G4 Equestria. The Draconequi function similar to Shiva the Destroyer, demolishing the aging universe to clear space for its recreation. Discord apparently liked his job too much and started destroying for the sake of destruction. Anarchy implies the Alicorn's job is the "recreation" side of the coin.
The Blank Wolf destroying Makarov and the Master causes these as well, but it's stated in its case it's repairing the damage rather than erasing the timeline.
Crossover: The original My Little Pony TV Specials, My Little Pony And Friends, My Little Pony Tales, and My Little Pony G3 all play some role in the story. Due to the Rainbow making Paradise Estate Ponies immortal until they left willingly, the Paradise Estate group who fought Discord during his first reign was composed of characters from the first three. Pinkie Pie is LITERALLY G3 Pinkie, and G1 Applejack was the Bearer of the Element of Laughter when Applejack called for aid from her alternate selves. However, so far there hasn't been a total team up between all the groups, so it isn't a Crisis Crossover just yet.
Create Your Own Villain: Back when she was still in her A God I Am phase (before mellowing out a lot), Luna gave Tirek the Rainbow of Darkness so he could try and prove his love to her. During her and Celestia's reign, Tirek returned to life and ended up having a battle with her for dominion over the night.
Celestia didn't make Discord a monster, but she taught him how to plan and ultimately accidentally helped him discover he was a sadist. She also left him to be punished by his family for helping her bring the Windigos to Equestria, causing him to keep a grudge against her.
Crisis Crossover: The G1, G2, G3, and G4 (pre-Reign of Chaos) Mane Casts are all brought to the present by Twilight the Unicorn during the Final Battle of Dark World, each using a set of Elements (along with the present mane cast and the Princesses) to defeat Nightmare Eclipse once and for all.
Implied to be what it took for the entity that would become Makarov to be defeated for the first time in the Realm of Legends where it took the form of an Alicorn Princess. While the actual battle is unseen, she's shown to have taken an army of fictional characters including Paul Bunyan and Daring Do to defeat and restrain her so Pandora could remove it's stolen Lights and seal it away.
Cruel and Unusual Death: After kicking one of his teeth out, Discord becomes so enraged at Mimic that he lacerates her with the tooth before finally slamming her into paste.
Literally every single death in the Transitions arc.
Cry for the Devil: "Everkind Forest" makes the zombie ponies from Story Of The Blanks seem downright tragic. The Princess Gaia brainwashed them to forget their actions, but whenever they look into Applejack's eyes, they remember. Their reaction is just heartbreaking.
Origins manages to invoke this for freakin' Discord! In the the later chapters, it's revealed that, in order to reach Equestria, he incarnated himself as a mortal draconequus born to G1 pony Shady; she raised him like a mother and it was heavily implied that, growing up, he wasn't anything worse than mischievous and actually got along well with Celestia and Luna when they did the same. More to the point, when his spirit starts to awaken, he is utterly terrified of it and actively resists it happening for a time. It's made all the worse because we, as readers, know he's going to fail.
There's also the Dark World!Mane Cast vs. Discord's army ofMooks. It's so one sided Rarity and Applejack manage to have Casual Danger Dialog while kicking flank. Special note goes to the Shadow-Beast-Of-The-Third-Unresolved (which was probably the most normal thing there) and the giant-cyborg-spider-vampire neither of which even get to attack before getting taken out by Pinkie Pie pulling an Offhand Backhand with her party cannon and Apple Pie using a Logic Bomb respectively.
Shortly before that, we have Proto-NightmareTwilight vs Angry Pie. The battle is extremely one sided and by the end, Twilight, after being brought back to her senses, is left wondering how many times over she would've killed Angry Pie if she weren't immortal and Angry is left near catatonic.
In Melody's '7 Dreams/Nightmares' chapter Rancor, while visiting the past, gets out of hand and Mortis, who's watching her at the time, has to step in. He easily disables her by paralyzing her with acupuncture in a couple seconds.
In the second half, Melody's daughter, Sweet Music, steps up to defend a unicorn named Spell Circle from three colts who are bullying him. Despite being a blank flank filly, she beats the crap out of all three and sends them running home with a warning that if she catches them doing it again, she'll tell everypony in town they got beat up by a girl.
The Dark World!Mane Six's first encounter with Paradox's Psycho Rangers ends with everyone but Twilight disabled in one hit each and ends the chapter on a cliffhanger.
Makarov does this to Natasha and Thunderchild in 15, simply dodging the former's sniper round and redirecting the latter's lightning bolt at her, before blowing up his thundercloud with a BFG (though both survive). This prompts Cadence to power up using the bonds of Misfit Actual and the Rebels and return the favor.
The Wolf vs Makarov/The Shadow Of Chernobull. Makarov makes it flinch once and the Death Dome slows it down briefly...that's it. The rest of the 'fight' is the Wolf ripping him to shreds and his blows failing to even hurt it.
The Blank Wolf verses anything is normally one of these. We see it have to deal with another Parody Sue, Incubators, and it's implied to have dealed with other beings. None of them last more than a couple minutes against it. Shining only survives his encounters via quick thinking and running for his life. The only reason it loses in the end is Cadence Taking the Bullet for Shining results in it being stripped of its immortality, and even then it doesn't go down with a big fight.
Cursed with Awesome: Fluttershy Sharing a Body with Fluttercruel isn't nearly as bad as it sounds. Fluttershy quickly catches on to how useful having a second, more assertive person to help her out in difficult spots can be.
Cut Away Gag: During the battle between Dark World!Spike and Rancor, Rancor says that Spike would make a good Champion for her. Spike asks who'd want to be her champion and it cuts to a pony version of Lobo fighting Superstallion in a city, implying Lobo is one of Rancor's Champions.
Later, Dark World!Discord asks Pinkie to marry him. Pinkie turns him down, saying it'd take a zillion years for her to reform him. The scene cuts to an Alternate Universe a zillion and one years later where Discord gives up evil and kisses his wife.
Cuteness Proximity: Pinkie Pie can't resist Filly Zecora's cuteness. While the others don't gush like she does, they do find her extremely cute.
Cut Song: Rarity had a song written for her by one of the Beta Readers to be used in "Pearl Necklace", but the author ultimately couldn't fit it in and included it as a What If? scene. It's a reprise of "Art Of The Dress" covering her relationship with Diamond Tiara that would be used to get through to Pinkie.
Daddy's Little Villain: Epilogue!Fluttercruel is this to Discord; she's the loyalist of the discorded Mane Six, and he in turn refers to her as his "little princess" and actually cares about her, to the point of ordering her to retreat from a fight with Queen Cadence because the latter is powerful enough to actually harm her.
Fluttershy quickly realizes that just because Fluttercruel was made by Discord doesn't mean she's evil like him. She's right.
"Applejack's Dream" implies that Liarjack becomes an Element Of Kindness in the Bad Future. We finally see this come to pass in Dark World.
Maasailand is Dark Is Not Evil: The Country. The red and black color-scheme and scorpion motif? In their culture they're symbols of love and peace and the Brotherhood of the Scorpion are actually pacifists. Even their Manticores are cute, docile, and vegetarians. It just happens that symbols of evil in most cultures happen to be symbols of good and peace in theirs.
The Dark Side Will Make You Forget: Twilight Tragedy and Rarigreed had both forgotten the ones they once loved while being controlled by Discord in Dark World. Whether it was Discord's brainwashing or their own way to cope with it isn't known.]
Fluttercruel gets one of Fluttershy's "So Many Wonders" song... Sort of. While it's not as sweet as Fluttershy's version, it's far from dark.
Fluttercruel tries to sing Fluttershy's lullaby in a desprate attempt to snap Fluttershy out of her Nightmare mode, but doesn't get the chance.
Princess Gaia's Villain Song is a true Dark Reprise of "So Many Wonders", this time being used as a siren's song to hypnotise Applejack. Instead of focusing on how wonderful the world outside is, it's focusing on happy they'll be by forgetting everything and coming to join her in her Lotus-Eater Machine forever.
Made even better when we discover she's lying to herself about what she is as much as everyone else.
Deadpan Snarker: The Equestrian Royal Guard suggests this as the appropriate response to certain circumstances;
Shining Armor: ...the Royal Guard Regulations state in Rule Four Hundred and Nine, that 'in face of overwhelming stupidity, an officer is permitted to deploy sarcasm'(I appreciate the Princess' understanding of our position).
Deal with the Devil: Diamond Tiara made one with Discord to carry out a ritual in order to free him. What was his side of the deal hasn't been revealed just yet, but given who he is, it's unlikely she'll get what she wanted out of the deal.
It probably has something to do with her insane mother Golden Tiara aka Screwball, who was the only happy pony during Discord's brief reign since to her the world finally made sense.
Celestia made one with Entropy, Discord's mother, to get the means to end hatred on Earth. The only thing she COULD give Entropy was the memory of an alicorn had to come crawling to her for help. Unfortunately, while Entropy didn't exactly trick her, the reflections provided to carry out her desire ended up becoming the Windigos to acomplish Celestia's wish.
Death Faked for You: While they thought Trixie had already left, the two Changelings who were sent to kill Trixie couldn't bring themselves to condemn a completely innocent pony to death (on top of an existing Heel Realization) and instead faked her death by killing a stray cat and giving the bloody knives to their superior.
Death Glare: Fluttershy's Stare, as expected. She can also use it as Nightmare Whisper. Unfortunately for her, so can Fluttercruel.
Decon-Recon Switch: While the fic deconstructs the simplicity and easy answers inherent in a children's show, the central themes of the series such as The Power of Friendship and the value of honesty, generosity, laughter, loyalty and kindness are constantly reaffirmed even after having seemingly been torn down.
It also deconstructs the "the three pony sub-races are now in harmony" aspect of the show's Hearth's Warming Eve play. The actions and attitudes of Onyx Tiara and Silver Spoon's mother show that many, many Earth Ponies are still very bitter over how the Unicorns and Pegasi once treated them.
Then reconstructs it by revealing its not as widespread as Onyx acts like it is and Silver Spoon's family were mainly humoring Onyx, and Onyx eventually realizes his racism nearly ruined his life.
"Retcon-struction", ironically, deconstructs the events of Lesson Zero. Twilight has been mentally torturing herself out of guilt for the riot she caused and desperately tries to make up for it, even after everypony already forgave her. It takes getting called out by Silver Spoon and a heart to heart with Trixie before she finally lets go of her guilt.
Pretty much every chapter of the original Reharminozation series involves deconstructing the whole "and everything went back to normal" ending of Return of Harmony. Fluttershy is confronted with the fact that Fluttercruel is now an entirely new entity and resolves to raise her herself. Rainbow Dash is haunted by her decision to abandon her friends and is completely unable to understand why they just welcomed her back as a friend so quickly. The whole Tom incident has given Rarity a severe, crippling fear of all things related to gems, diamonds in particular. Applejack becomes obsessed with telling the truth. Pinkie becomes so obsessed with parties and happiness that she puts her mental and physical health at life-threatening risk. Trixie is so affected by Discord's Breaking Lecture that the World-Healing Wavehad no affect on her at all, and even after everything was restored, she remained so catatonic that she literally couldn't survive on her own and needed to be cared for by her family like a paraplegic vegetable (Though this turns out to be mainly due to Loneliness possessing her). Twilight's Sanity Slippage in "Lesson Zero" is made into having been because of Discord's torture of her. However, being a Decon-Recon Switch fic, they all recover and turn out stronger for it.
Defeat Equals Friendship: After being browbeat into submission, Fluttercruel becomes a valuable ally for Fluttershy. Even when she takes control, she's not outright mean and cruel to Fluttershy, she just wants to actually enjoy life for a change.
This pays off during the battle with Nightmare Whisper, as Fluttercruel cares enough about Fluttershy to return from beyond to save her.
To some degree, this applies to Trixie learning to accept the Mane Cast's friendship.
The Cutie Mark Crusaders attempt to do this with Silver Spoon. Thanks in part to the Princess Gaia incident, they succeed.
Defusing the Tyke Bomb: This is what Fluttershy does, teaching Fluttercruel that she is so much more than a cruel parody of Fluttershy.
Despair Event Horizon: Twilight after her memory spell backfires on Nightmare Whisper, forcing her to experience all the suffering and pain Nightmare Whisper had absorbed. Trixie pulls her back with the memory spell. It then turns out that Nightmare Whisper can fire a beam of pure suffering from her mouth to make anyone it hits experience this, which she uses on Rainbow Dash. Thankfully, the memory spell works again that time.
Determinator: The entire mane cast during the Final Battle with Nightmare Whisper. Absolutely nothing will stop them from saving Fluttershy. Trixie gets electrocuted and has a rib broken, Applejack gets glass daggers lodged in her back, Pinkie Pie gets cut up being thrown through a stained glass window, and Rainbow and Twilight both end up getting Mind Raped, but refuse to quit. But Rarity takes the cake by using telekinesis to keep moving after having her legs broken!.
Also,Diamond Tiara resists Princess Gaia's song through willpower and Self-Deprecation, though it's encouraged by Discord shouting into her mind.
Discord: "IGNORE IT! ONLY BAD LITTLE FILLIES WHO DON'T CARE THAT THEIR MOTHER STAYS SICK FOREVER LISTEN TO THAT SONG! IGNORE IT! YOU ARE NOT TO THINK ABOUT IT OR PAY ANY ATTENTION TO IT AT ALL!!!"
Silver Spoon will find and save Diamond Tiara. Not even being Mind Raped by her Nightmare can stop her.
Did We Just Have Tea with Cthulhu?: Ponythulhu is surprisingly polite and friendly for an Eldritch Abomination, to the point Dark World!Twilight makes a note to be friendly to send him a friendly note after throwing the blackbirds that spent the last 1000 years torturing Derpy into his realm, providing him with a recipe for them.
Shining Armor once set in to a diplomatic meeting between Celestia and Queen Tiamat. He comments how surreal it was to witness the sun goddess having a polite conversation over tea with a five-headed dragon so massive her tea cups are bigger than most buildings.
Did You Just Punch Out Cthulhu?: The mane six's previous defeats of Nightmare Moon and Discord, of course, but they add two to the count with the defeat of Nightmare Whisper and Applejack teaming up with five alternate versions of herself to defeat Nightmare Mirror.
There's also G1 Mimic managing to bust out Discord's tooth permanently and perform a successful You Shall Not Pass. She may have died, but she still managed to wound him in such a way no one has been able to do before or since.
Pinkie and Minty managed to defeat Princess Luna with a musical number during the Cosmic Retcon of G3. Even though Strife had weakened her, that's still a great accomplishment.
Cadance managing to defeat Havoc's Avatar. It may not have been NEARLY as strong as the real thing, but that's still impressive.
The Paradise Estate Ponies, even taking into account they had three Alicorns supporting them (all three were considerably weaker than him), managed to defeat Discord in a straight up fight with the Rainbow Of Light. Unfortunately, Galaxia decided to shatter him, allowing him to Body Surf into a new body.
Dark World!Spike manages to get the upperhand on Rancor, the Draconequus of Violence, Passions, and Anger, and force her into retreat temporarily. She is a young Draconequus, but still.
There's also an Alternate Universe Rainbow Dash being shown killing Pinkie's Nightmare, Nightmare Granfalloon.
The Dark World Mane Six managing to defeat Odyne!Cruelty, first destroying her body (unfortunately killing Sparkler in the process), then by blasting her soul with the Elements, banishing her from mortal reality.
One that occurs offscreen was a mortal Pegasus, armed with the Concept Killing Spear, managed to kill the demigod Cupid, permanently due to having a personal hatred of love. Unfortunately for said Pegasus, said demigod was the son of Venus, who descended to the mortal plain in an Unstoppable Rage...
Bright Eyes manages to defeat Discord's older brother D___t in a sword fight and kill him Deader than Dead. True, it was simply his Shadow of Existence, but its still no small feat and is implied to have possibly saved existence from an insane Concept coming back into existence.
There was also Dark World!Discord forcing Nightmare Paradox to endure several thousand pictures of him mooning himself in the mirror set to a loop while Twilight sees his memories from the Memory Spell. While this did help Twilight by not letting Paradox see what memories she got (causing her to be more cautious in the fight), it seems Discord mainly did it just to piss her off after enduring an And I Must Scream fate at her hooves for so long.
There's also one of the fics' iconic moments when G1 Mimic pulls off a You Shall Not Pass on Discord. She knows its going to get her killed, but does it to let the others including Celestia and Luna, her daughters get away. She then exploits this trope by telling Discord the way to Earth has been destroyed, trapping him in Equestria, causing him to have a Villainous Breakdown that gives her an edge. Her last words also qualify, as after shattering his tooth permanently, she spits his own claim she wouldn't be able to scratch him back in his face before he kills her.
Disability Immunity: Laughter!Applejack's world's version of Pinkamena has multiple personalities (though apparently in a far more stable form), which rendered her immune to the Stallions In Black's memory wiping spell, as the other personalities would remember what the one that got wiped forgot.
Disc One Final Boss: Loneliness serves as the main antagonist for the story arc about saving Trixie but meets her end when Trixie breaks free and accepts her Element Of Magic. Before the chapter is over, Discord has been freed from his prison once again to take over as the main villain. However, before they have to deal with him, Princess Gaia serves as the Big Bad for the penultimate story arc.
Divine Intervention: The Fires of Friendship that destroyed the Windigos was Fauna Luster lending Her power when Clover, Smart Cookie, and Pansy forged a friendship in spite of their impending deaths and the racial hatred so prevalent in their world. According to Celestia, while Fauna Luster always has Her power offered, very few mortals have ever managed to actually open the door for Her to intervene. Also, the Elements of Harmony use The Power of Friendship to tap into Her power as well.
After most of the Breezies are taken directly to Heaven by Abbatissa, the Alicorn of Prayer, Zipzee and Daisyslow want to send Breezie Blossom, their home, with them. Abbatissa tells them to pray, which they do, and their prayers are answered.
In a way, Dark World!Discord's Backup from Otherworld moment qualifies, seeing as he is a God and did so using his brother's aid.
General-Admiral Makarov believes he's succeeded in becoming a God and thus beyond the reach of the Wolf. He spends a few minutes taunting it and punches it in the face. It replies by slashing him, causing his stolen lights to begin leaking out and ultimately erases him from existence. Granted, it was going to erase him anyway, but he probably didn't do himself any favors clopping it off.
Doomed by Canon: Inverted. After Applejack stares into the pool of Truth and gains the ability to discern lies at a glance, Luna makes it pretty explicit that her sense of Truth will drive her nuts if the canon timeline diverges too much from the POV-verse. Fortunately, that's taken care off by the Crisis Crossover of all the other staple AJ's of the multiverse teaming up and taking out the most evilest AJ with alternate AJ's based off of the other Elements of Harmony.So that happened.
Part one of Chrysalis' origin story ends with Chrysalis slaughtering her entire home village to hide her existence and defeating the witch doctor that tried to end her reign of terror before it could truly begin.
Dragged Off to Hell: The ponies from Sunnytown are dragged back to the town's boundaries in this fashion.
Almost happens to Dark World!Applejack when Shadows of Oblivion try to drag her to Entropy's Realm.
Dark World!Discord is ultimately dragged off to Entropy's realm through the wound Rancor left in him. Though, by his words, he may consider this a better fate than the one he was presently experiencing.
Queen Chrysalis' Co-Dragons appear to be General Hercules Beetle and Digger Wasp. Even though she demotes Hercules and makes his brother Goliath General, the story still focuses on him out of Chrysalis' changelings and Digger Wasp was key to her plans working. Both are shown to answer directly to her.
It turns out that Professor Kabuto, who seemed to simply be the Evil Genius of the group, is actually on this level due to enhancing himself heavily through his experiments. He's not only important to her over all plan (being the only Changeling who understands the rune), but powerful enough Queen Chrysalis made him a trap onto himself.
Dramatic Irony: Twice now the readers have known something about the current Big Bad the characters don't, such as Fluttershy becoming Nightmare Whisper and Discord's plan to escape.
During "Modern Major Evil Overlord", the story crosses over with one of the Recursive Fanfiction pieces when Twilight Tragedy inadvertently redeems an alternate universe's Discord. Anyone who read said fanfic will recognize the scene, but Twilight has no idea she's doing anything more than thinking to herself.
During the next chapter "Lemons N' Flint Rocks", has it as well, in a similar fashion. Apple Pie is talking with Twilight Tragedy, but has no idea she is, as Tragedy is disguised as an Earth Pony filly named Half-Light Dawn. She unknowingly, thinking she's just talking to a normal filly, ends up triggering a Villainous BSOD in Tragedy.
Drunk on Milk: Saltwater apparently has the same effect on ponies as an alcohol. In the "Black Pearl" chapter, Fluttercruel/Fluttershy end up getting drunk on it, in part because Fluttershy doesn't drink normally. It's revealed the next chapter that they drunk so much that it would've gotten Princess Celestia drunk!
Dungeon Bypass: Attempted in Dark World when the heroes try blasting Discord's castle from a distance with the Elements of Harmony. It simply sprouts legs and runs away. Double Subverted in that they convince it not to hinder them.
Dying Moment of Awesome: This universe's version of Mimic was killed fighting Discord when he appeared in Equestria for the first time, knocking out his tooth in their fight. According to Princess Luna, she's the only one to ever successfully injure Discord in battle, and she didn't even have the Elements Of Harmony.
A previous loop that saw Trixie become an Alicorn. While Paradox defeated and likely killed her, Trixie went down fighting and left a Wound That Will Not Heal in the form of a fourth degree burn on Paradox's face that's the reason for her White Mask of Doom.
Saharnoj Vaty, the third of Makarov's Alicorn Cyborg Co-Dragons, managing to fight off Makarov's control with The Power of Love she has for her sister long enough to self-destruct and destroy Makarov's Skyfall weapon. As the Interviewers point out afterwards, she beat Makarov in the best way possible: by proving he was wrong to believe love was weak.
Dima sacrifices himself to save Gilda's life when Makarov attempts to kill her as part of his 'script'. Realizing he's crippled even if he survived, Dima refuses medical attention so he can ruin Makarov's planned climax with his death in order to enrage and weaken him. The result enrages Makarov so badly that for a second the entire base flickers and Makarov suffers a temporary Glamour Failure. When Makarov appears again, for the first time in the entire story that Makarov's composure doesn't suddenly snap back to confidence and he's still in a psychotic rage.
Sunset and Ranger die saving a pilot's life while helping stop a megastorm that's threatening Caruba, Sunset dying in the process of trying to save Ranger's life. They're even awarded a Solar Horseshoe and a Lunar Horseshoe posthumously for their actions and Celestia has them buried in the royal catacombs with Equestria's heroes.