Fairy Tail has a few of these like Chapter 134 when the Oración Seis takes out the entire guild alliance and Chapter 169, the beginning of the Edolas arc.
The ending of the Edolas arc too. The heroes are back home, having sorted everything out and patting each other back when, "Oh hey, what's the Alternate Universe counterpart of the dead childhood friend doing here?"
And again in Chapter 215, where we learn Master Hades, the leader of Grimoire Heart, is the previous master of Fairy Tail.
To go into further detail: In Chapters 215 & 216: When the series Big Good, Makarov, whom many thought was the strongest character in the series was easilydefeated by the next Big Bad Master Hades. Hades also reveals that Zeref is "the essence of magic."
The latter is repeated again but in reverse when after Hades suffers his own nasty defeat, when low and behold the previously angsty and self-loathing Zeref shows up and, all the while freezing Kain Hikaru and Rustyrose with only his presence, reveals that he has been "awake" all this time, that he values human life as opposed to everyone believing him to be the Big Bad of the series, and that he sees Grimoire Heart and Master Hades as nothing more than trash. He then promptly finishes off Hades for good with one attack, before turning around, feeling something far worse coming over the horizon...
And that something turns out to be the black dragon that kicked Gildarts' ass. The dragon then proceeds to utterly devastate the Fairy Tail mages before destroying the island.
In Chapter 221, apparently Grimoire Heart intends to use Zeref to kill all of the muggles in the world and remake it as a world of wizards... and they've just caught the final ingredient
In Chapter 235, Azuma uproots the entire Tenrou Tree, and it is revealed its magic was boosting Fairy Tail's magic, and keeping them alive under the Kin's onslaught. In other words, with it gone, not only are the Fairy Tail wizards being further drained of magic, but it also heavily implies that Makarov and Mirajane really are going to die now.
And Chapter 253... Oh My God, the 253rd Chapter... To elaborate, Acnologia destroys Tenrou Island seemingly along with the entire core cast and many extras, and then has a 7 year time skip. Watch out for the wall!
Note that all of the above happen in the same arc. More like a Wham Arc!
Personal Wham for Lucy in Chapter 256: Her father has been dead for an entire month.
Chapter 297: Glimpses of the near future tell that something quite catastrophic is about to happen. And quite a few people will die from it too...
Chapter 300: Jiemma kills Lector. Sting blasts a hole though Jiemma.
Chapter 301: There was once a Dragon Slayer. That Dragon Slayer killed many Dragons and bathed in their blood. He gradually turned into a Dragon. He is now the Dragon King. That Dragon is Acnologia.
Oh yeah and he possibly had some help from Zeref.
Arcadios and Yukino meet Lucy and the Dragon Slayers.
Chapter 312: The hooded person is from the future...and it's Lucy.
Chapter 314 has a big reveal, as we finally find out why Kagura hates Jellal so much. She is Simon's little sister, wishing to kill Jellal to avenge her brother. And when distraught Erza points put that Simon's death was actually her fault, Kagura slowly pulls out Archenemy...
Chapter 315: Erza saved Kagura from being kidnapped by Zeref's cultists when they were younger.
Chapter 316: Future Lucy wakes up and starts sharing details on what happened. It then crosses over to the Princess who expositions several details, including the apocalyptic event that occurred in the future: The Bad Future will be caused by a herd of 10,000 dragons on their way to attack Fiore and will leave the kingdom in utter ruins.
Chapter 323: Lucy isn't the only person who came from the future, there's also Future!Rogue who was possibly hiding in Present!Rogue's shadow. It Makes Sense in Context.
Chapter 324: We learn that Future!Rogue is from 7 years in the future and that he's on a mission to eliminate the person who will close the Eclipse Gate and lead the country to its destruction. This person is none other than Lucy and as Future!Rogue rushes in for the kill, Future!Lucy makes a Heroic Sacrifice and takes the blow straight on.
Chapter 327: It turns out that due to certain circumstances, the Eclipse Gate, isn't what will save Fiore. Rather, it's what will bring its destruction via 10,000 dragons.
Chapter 333: Present!Rogue finds out that his future self is the one responsible for the destruction of the country and the despair of everyone around him. To make matters worse, Ultear is determined to kill Present!Rogue in order to return everything back to the way it was.
Chapter 334: Gray gets shishkabob-ed by multiple mini-dragon blasts. And it looks like he's going to die....
Chapter 335: Ultear sacrifices her life energy to reverse time back to before the Eclipse Gate opened. It only sets time back by one minute, but this is enough for Gray to dodge the blasts that would have killed him, as well as giving the heroes a chance to turn the tide of the battle to their advantage.
Chapter 337: With the Eclipse Gate destroyed, everything starts unwinding itself, but Mavis is concerned that none of the Dragon Slayers were able to defeat a single dragon. A more potent wham episode is that Future!Rogue informs Natsu that in a year's time, Frosch will be killed.
Chapter 339: Cobra plans to break the Oración Seis out of prison and it's heavily implied the old woman Gray, Jellal, and Merudy encountered was an older Ultear.
The bigger whammy is that it has been confirmed the two know each other. Many fans saw it coming, but to finally see it confirmed is something else.
Chapter 342: The guild encounter the 4th strongest Wizard Saint, who was one of the founding members of Fairy Tail.
Chapter 343: Minerva is back and this time, she is a Dark Guild member.
Chapter 344: Erza's been turned into a child.
Chapter 345: And now Natsu has been reverted to a child, and the one responsible is a member of Succubus Eye.
Chapter 348: Gray has been reverted to a child, and the mystery man mentions two key things: "The other side of the gate of Hades" and taking credit for freezing the village.
Chapter 349: Turns out the mystery man, Doriate, was lying about freezing the village, but then he reveals himself to be a demon from the Book of Zeref like Deliora and Lullaby.
Chapter 352: The Eternal Flame has been revived and his identity has been revealed. It's Atlas Flame.
To stress how whammy this is, NATSU MEETS A DRAGON FROM THE PRESENT!
Chapter 352 also cruelly subverts this: It is only a memory summoned by Wendy.
Chapter 356: Tartarus make their move, the Magic Council is wiped out and it is revealed that Tartarus is made up of demons from the Book of Zeref, led by E.N.D., the strongest of Zeref's demons, whom Igneel failed to defeat.
Chapter 358. Just when you thought this arc couldn't get any Darker and Edgier, Tempesta's Taking You with Me move creates the magical equivalent of a chemical weapons attack, killing hundreds of Hargeon's citizens and nearly kills the Raijin Tribe. It ends with Natsu promising a Roaring Rampage of Revenge.
Chapter 360: Jackal's power manages to defeat Natsu, who's been built up as nearly invincible at this point.
Chapter 363: We learn why Tartarus is slaughtering the Magic Council; the Council possesses a weapon called Face capable of nullifying all magic across the continent. This will leave all mages powerless, while Tartarus, using curses instead of magic, will be free to walk all over them. Three unknown former Council members are the living keys to the seal of Face, so Tartarus is indiscriminately killing every Council member until the three keys are dead.
Chapter 364, full stop. For one thing, the Oración Seis is back; turns out Doranbolt had to free them in exchange for Cobra's intel on Tartarus. He also hired Jellal and Meredy to keep an eye on them, knowing full well how risky of a move that is. And then we have Crawford Seam, the ex-chairman of the Magic Council and an all-around Fat Bastard who only very rarely made appearances in the series, return... as The Mole for Tartarus, who is now kidnapping Erza and Mirajane and delivering their unconscious bodies to Tartarus' HQ. And last but not least, Elfman may now be forced to sell his soul in a Deal with the Devil in order for Seliah to spare Lisanna's life. Darker and Edgier: The Arc indeed.
Chapter 365: As Erza is being tortured by Kyouka at Tartarus' HQ, we find out that two of the three keys to the seal of Face are already dead. The third key... is Jellal.
Chapter 368: We find out the details of Elfman's Deal with the Devil: He is being forced to install a lacrima bomb 500 times more powerful than Jupiter Cannon that will instantly vaporize Fairy Tail. What makes this worse is that he's fully aware of what he is doing, but because of Seliah's Macro he is unable to do a thing about it.
Jellal gets taken out by Zero.
Chapter 369: Zero ends up being an illusion created by Midnight. To counter this, Jellal blinds himself on purpose and takes out all of the Oración Seis with his Sema spell. After their defeat, he invites the members of the Oración Seis to join Crime Sorcière and defeat Zeref. At the same time, Crawford Seam, the former Chairman of the Magic Council successfully transfers Jellal's key to himself and before he can transfer the key off to someone else, he is unceremoniouslykilled off by KyoukaIn the Back. With his death, the seal on Face has been released. The chapter ends with a teary eyed Elfman setting off the lacrima bomb in the Fairy Tail guild hall.
Chapter 372: Zeref is residing in Tartaros' base.
Chapter 376: Wendy achieves Dragon Force!
Chapter 379: Hades is back, and gives Natsu a message for Makarov, that Face is not Tartarus's real target, and that it's time for Makarov to "let out the light."
Chapter 384: Lucy has no choice but to break one of her golden zodiac keys, but in the process is able to then summon the Celestial Spirit King.
Chapter 387: There's at least 2000 Faces!
Chapter 390: Silver is Gray's father...sorta, as he's a demon using the corpse of Gray's father as a vessel. The demon's name? DELIORA.
Chapter 392: It is revealed, that Silver had lied about being Deliora. He was in full control of his actions the entire time.
Chapter 399: A Big Bad and a Big Good reappear. More accurately, Acnologia returns, heading toward where Fairy Tail's fighting Tartarus. Shortly thereafter, Igneel appears as well, questioning whether the time has come for his return. This was our first confirmation that Igneel was still alive, possibly hinting that the other Slayers' dragons are still around as well.
Chapter 400: Igneel was inside Natsu the whole time. He promptly heads off to battle Acnologia.
Chapter 412: Face has activated and draining magic from all over the continent, but aid comes from an unexpected corner. Grandine, Metalicana, Weißlogia, and Skiadrum (the latter two we have been led to believe to have been dead) all appear and begin destroying each of the Faces, preventing magic's eradication.
Chapter 413: At last, Tartaros has been apparently stopped, and all that remains is to deal with END's Book of Zeref. Wait, where did it go?
->Zeref: "This belongs to me. I'll be taking it back, now. It's really important, you know."
And finally, the icing on the great big Darker and Edgier cake that is the Tartaros arc, Igneel is killed by Acnologia in Chapter 414. That's right: The goal Natsu had had throughout the entire seriesis made moot right in front of him, in the mosthorribleway possible. And to make matters worse? Zeref more or less confirms that he will be taking the role of Big Bad from here on out.
Chapter 415 gives us a Bittersweet reunion. The Dragon Slayers get to meet their Dragons once more and learn they made a pact years ago to watch over and protect humans well except for Acnologia. However this reunion takes on a grim reality. Acnologia managed to steal their souls forcing them to enter the bodies of the Dragon Slayers. They had to leave their hosts to stop FACE, however because of that they have to go away for good now.
Chapter 416: Fairy Tail disbands, Natsu and Happy leave for a year to train, and we learn what E.N.D. stands for: Etherious Natsu Dragoneel.
Chapter 424: Gray has joined Avatar and his demon slaying magic is taking over more of his body.
Chapter 425: Natsu fulfills his promise to future!Rogue by taking up Rogue's mission to destroy the Avatar cult. How does Natsu know this? Because there was more to future!Rogue's last request. Gray is the one who's going to kill Frosch!
Chapter 436 has a double wham: Natsu's revealed to have been created from the body of Zeref's dead younger brother. Acnologia is shown to be capable of taking human form and meets up with Zeref in a mountain cave, where he is challenged by the black wizard.
Chapter 439: The reason Markarov disbanded Fairy Tail was to protect the members of the guild from the super-militarized magical nation of Alvarez, who, ten years ago, attempted to invade Ishgar so they could secure Lumen Histoire. With the deterrent of the magic council gone, Markarov has gone to the west for negotiation, to buy time for the magic council to reform and figure out a way to prevent another invasion.
Chapter 440: The strongest mage in Ishgar has defected to the Empire.
Chapter 444: The Emperor of Alvarez, the nation trying to take Lumen Histoire, is Zeref himself.
Chapter 449: Mavis isn't just ageless, she has the same curse as Zeref, including the Instant Death Radius. The only reason it hadn't kicked in is because there was a war going on where she was a tactician.
Chapter 450: Mavis's Instant Death Radius activates, killing Makarov's mother after she gives birth to him. In order to avoid killing anyone else she forces herself into isolation until she meets Zeref again. However, just when it seems like they're going to try a shot at Eternal Love, Zeref's curse kills Mavis.
Chapter 465: It's not just Natsu who is over four hundred years old — it's all five dragon slayers who were raised by dragons. They are children from the past who were brought forth in time via the Eclipse Gate in order to kill Acnologia. The day their dragon parents "disappeared" was actually the day the children arrived to the current era. And the Celestial Wizard that opened the gate for them? Layla Heartfilia.
Chapter 470: God Serena, just revealed as a second generation dragon slayer with the lacrima of eight different kinds of dragon, and fresh off of cheesing four of the Wizard Saints, is literally punched in half by Acnologia.
Chapter 483: One of the two unrevealed Spriggans is Erza's mother. Or sister. Some sort of relative. And is as strong as someone who Makarov compared to Zeref.
Chapter 488: Gajeel is (most probably) dead...
Chapter 489: August obliterates Natsu's group, turning all of them into ashes, Mavis breaks free of her crystal, Eileen fights Acnologia on equal ground, and casually reshapes the world.
Chapter 490: Gajeel is alive! And at the end of the chapter, he meets one of the fairies of origin — Zera.
Chapter 493: The last Spriggan is a Dragneel.
Chapter 494: Mavis is captured and rendered helpless by Invel, while the bulk of Alvarez's army lies right outside Fairy Tail. Even better, all of the Spriggan 12 have gathered alongside Zeref in preparation for Fairy Tail and their allies to arrive, whether they've recovered from their wounds or outright been brought back to life by Neinhart's Historia.
Chapter 499: In order to stop an Involuntary Battle to the Death, Juvia and Grey kill themselves in an attempt to save the other. Grey recovers, but only because Juvia him a blood transfusion with the last of her strength, meaning Juvia is (again, most probably) dead.
Chapter 500: Juvia survives with Wendy's help, but Gray learns the Awful Truth: that E.N.D., whom he'd sworn to defeat, is none other than Natsu Dragneel.
Chapter 502: Natsu's illness was not caused by anti-ethernano tumor. It's something way, way worse...
Chapter 503: END is awake and hasn't forgotten about Fairy Tail. But then he finds Gray.
Chapter 505: Irene enhances the enemy Mooks, forcing Makarov to use up his life to wipe them out with Fairy Law.
Chapter 508: Larcade is Zeref and Mavis's son.
Chapter 513: Irene is Erza's mother and once the Queen of Dragons.
Chapter 514: Four hundred years ago, dragons and humans coexisted in Ishgar. However, the dragons of the western continent, as well as dragons who didn't want to coexist with humans, went to war with the humans and the human-supporting dragons. However, the human side was losing, and Irene, desperate to turn the tide of the war, invented Dragon Slayer magic. However, while the plan did indeed work, the power of Dragon Slayer magic began to cause side effects in its wielders; in particular, dragonification, like what happened to Acnologia...and Irene, while Erza was in her womb.
Chapter 516: After Erza and Wendy seemingly beat her, Irene successfully transfers her consciousness into a human body at long last. However, it's not with Erza like she originally intended, but Wendy!
Chapter 523: Acnologia shows up in front of Erza and Wendy.
Chapter 526: Larcade was never Zeref's son, he was just another book. Zeref and Mavis's real son is August.
Chapter 527: The Reveal, at long last, of Acnologia's Dragon Element. He doesn't have one. Specifically, he feeds off magic itself, which means all forms of magic, including Dragon Slayer Magic, can't hurt him.
Chapter 532: Mavis fails at her attempt to stop Zeref, which was to try to talk Zeref down. Instead, Zeref extracts Fairy Heart's power from Mavis and takes it for himself, rendering Mavis in a unconfirmed state.