World-Healing Wave

They said it was lunacy, investing in Mordor real-estate. Well, who's rich now?!

"It's like the Nothing never was!"

—Bastian, The Neverending Story

The good counterpart to the World-Wrecking Wave, the World-Healing Wave magically repairs a setting of any and all destruction done to it by evil forces. It can have a lot of different causes: the heroes may be returning the Cosmic Keystone to its proper place/owner, the Fisher King is healed, the God of Evil is slain and their Walking Wasteland effect is undone, the players reset the computer system, or a God of Good uses a massive display of Fertile Feet and Green Thumb to restore the place.

For extra warm and happy feelings, any people, plants, animals, and structures killed and destroyed may be brought Back from the Dead and/or magically repaired.

Needless to say, a World-Healing Wave is a HUGE Deus Ex Machina that can remove all worry from a plot. "So what if the Big Bad killed Danny, burned down Troy and kicked Skippy? If the heroes succeed he'll be resurrected!" Which is why the heroes will likely have it as the objective of their entire quest, and it's usually limited to kid stories to provide expedient Disney Deaths. It can also be justified, if the Cosmic Keystone or what-have-you that caused this event really is that big a deal.

Anime and Manga

The ending of Green Legend Ran anime results in this. For decades the Earth had been reduced to a wasteland due to an alien influence, and when the Big Bad was finally defeated, Ran and his Magical Girlfriend magically restored the Earth back to what it used to be.
In Miyazaki's Princess Mononoke, When the Forest Spirit's head is shot off, its body spews a goo that destroys everything in its path, as a classic World-Wrecking Wave. After the heroes return it, the goo vanishes, and new plants sprout up from the ground, over Irontown... even the lepers are healed. But there's a price - the Forest Spirit is gone, now, and will never return.
At the end of RahXephon, it is revealed that the instrumentalist can create a world according to their will. Ayato's choice creates a world where all the people he loves are happy, and the Mullian war never happened.
The ending of the first season of Sailor Moon. It's also implied that Crystal Tokyo is herald in when Neo Queen Serenity ascends and pulls one of these for the entire planet after some global freeze/disaster.
The plot of almost every Dragon Ball story arc inevitably involves using the Dragon Balls to generate one of these.
Yukio Oikawa does one at the end of Digimon Adventure 02 by using the power of a world were dreams come true to convert himself into energy and revitalize the Digital World. Justifed at least in this case because, as the way he did it was previously explained.
- In Digimon Frontier, the world was in disarray because bad guys had stolen important data. We sometimes got to see ruined areas restored after the fall of the Monster of the Week early on. In the final episode, the entire Digital World had been fed to the Sealed Evil in a Can to fuel his full restoration, and he plans to make a new world in his image. When he's taken down for good, we get to see an entire world - the Digital World in its natural state, seen only in flashbacks until now - form from shiny barcodey lights.
At the end of Kanon, Ayu's miracle undoes all the tragic deaths occurring earlier in the series and heals Akiko.
- In Clannad, there's a smaller version of this. The Girl from the Illusionary World manages to use the Orbs of Light brought by Tomoya (as the Garbage Doll) to cause a Retcon; it saves Nagisa from her Death by Childbirth and Ushio from her illness, while also healing Fuuko from her coma.
Also used in Mahou Sensei Negima, when the newly released Asuna uses her sword and Code of the Lifemaker to repair the damage done to Mundus Magicus (which was gradually being erased) and bring back the people who have been erased before.
In Puella Magi Madoka Magica, this is, more or less, the result of Madoka's wish in the final episode. Magical girls and others who are killed by witches get brought back. Magical girls who became witches, on the other hand, are whisked away to Magical Girl Valhalla by Madoka at the moment when they would have become witches. Madoka herself is removed from existence because she would have become an even more powerful version of Kriemhild Gretchen otherwise.
In D.Gray-man, having the Musician play the piano in Noah's Ark reversed the download which restored the setting as well as all the characters who hadn't been killed in battle.
The mission in Uchuu Senkan Yamato is to bring back a device that will repair Earth's wrecked biosphere. The oceans have been boiled away, the planet will be completely unlivable and humanity extinct in less than a year, but once the ship gets back with the device....

Fan Works

With Strings Attached: When the Hunter stabs the Heart of Evil on the Plains of Death, it releases a massive, ball-shaped burst of energy that spreads out over the Plains, destroying all the undead massed there and triggering rain in clouds that had been sitting there for ten years. Later, Ringo notes that some old seeds in the ground have started to sprout.
Fallout Equestria has The Gardens Of Equestria Twilight Sparkle's greatest creation, a megaspell powered by the Elements of Harmony able to cleanse all Equestria of all the radiation and taint created by the end of the war and return it's ability to be a paradise again.
The first Symphony from the Symphony of the Sword cycle of Undocumented Features reaches its climax when the Cephiran Trinity -- Corwin, Utena and Anthy -- revolutionizes the world of Cephiro. It doesn't bring all the good guys back to life, but most of the world's physical damage is fixed.
Appears twice in the 1990s-vintage Mega Crossover fic The Dance of Shiva by John Biles:
- During a dream excursion in chapter 13, Linna and Priss witness Serenity and four companions trigger one which is solar-system-wide and essentially the beginning of the Silver Millennium.
- After SHIVA has been defeated, Nene is divinely empowered to undo all the damage caused to Mega-Tokyo in the conflict. People actually perceive the Wave as immense phantom representations of her hands moving through the city, healing individual wounds, repairing entire destroyed buildings, and even stopping explosions in progress.

Film

The end of the Buzz Lightyear of Star Command Movie has Buzz convert Zurg's World Wrecking Wave into one of these by using the force of his will and the Power Of Good to undo Zurg's corruption of the LGM's Phlebotinum.
Cloudy with a Chance of Meatballs (The Movie) does this at the end—the clouds over all the world's cities disappear in a magical wave.
In the original Tron, when the MCP was destroyed all of the red lines in the landscape turned to blue (indicating the end of the MCP's influence) and all of the I/O towers lit up, showing that programs could communicate with their Users again.
At the end of The Neverending Story, when Bastian started making wishes Fantasia was recreated the same as it was before the Nothing destroyed it.
At the end of The Matrix: Revolutions, the entire Matrix is returned to normal using a cool sci-fi effect and the requisite black cat.
The earthquake resulting from the restoration of the Earth's core to its normal spinning state in The Core is described by DJ Qualls's character as "one giant shock wave" in which "the Earth is healing itself!"
Sgt Peppers Lonely Hearts Club Band. The wave of goodness that passed over the town of Heartland at the end of the movie, canceling out all of the effects of Mr. Mustard's corruption.
In Star Trek II the Wrath of Khan, the Genesis Device is a World Healing Wave weapon. When fired at a planet, it converts the matter on the surface into life-sustaining matter, in effect terraforming the entire planet in days instead of years. It is shown to have worked on a cave, and in the end it is detonated in a nebula, building an entire planet from scratch. Star Trek III: The Search For Spock, however, shows that it doesn't actually work. Said planet goes through its entire lifecycle (from newly formed planet to catastrophic destruction) in what is implied to be a week or two at most. This because its lead creator, Captain Kirk's son David Marcus, used unstable protomatter in order to basically cheat his way into completing the thing, showing he's Not So Different from his father.
- The trope is also subverted in that Genesis doesn't discriminate in what it converts. Whether dead rock or populated planet, everything on the surface is getting culled for Genesis to do its thing. This becomes a big issue in the next few movies, because Genesis represented one of the deadliest weapons known to civilization: a weapon that could not only kill all life on a planet, but leave a perfectly healthy biosphere behind for whoever did the killing (or at least do the first part when they discovered how unreliable the creation part was).
- Worse, it may actually work just fine. It was meant for use on dead planets, not what specks of matter it could pull together from a nebula. Apples and oranges, only more so. Though shortcuts were taken, (and for a casual fan, there's no knowing where the Expanded Universe stands on the matter) from what we got onscreen, a warning label on it that says "actual planet required" may be all that is necessary for the thing to go operational. It would be very bad if misused.
A Troll in Central Park has one at the end, with Stanley repairing Central Park after it was destroyed by Gnorga's World-Wrecking Wave. But he takes it too far, covering all of New York City in flowers, which would bring one of the most important cities in the world to a screeching halt and have a devastating effect on the ecosystem.
Yellow Submarine. As the Beatles sing "All You Need Is Love", all of the things destroyed and people frozen by the Blue Meanie attack are restored to wholeness/life.
The Sprite from the "Firebird Suite" segment of Fantasia/2000 uses her Fertile Feet to restore the ashen landscape after the devastation brought on by the Firebird.
After the Beast transforms back into the prince in Beauty and the Beast, magical sparks spread across the castle and transform it back to its original state, with the gargoyles transforming into angels and the darkened walls turning to alabaster.
The end of South Park the movie has Satan use one of these to restore the world (or at least North America), including bringing everyone back to life. Except Kenny, who has to go back to being dead.

Literature

In the end of Good Omens, Adam makes it so that the world will not remember the day that just passed and all that happened is undone: the Book shop did not burn, the Bentley is new again and no one died.
Semi-example at the end of the Mistborn trilogy, after Sazed ascends to godhood all the damage that the Lord Ruler and Ruin did to the world is fixed, the ashmounts get sealed up, and there are flowers. It's only a semi-example because he hadn't figured out how to bring dead people back to life, so most of the original population is dead, but at least the survivors are safe and get a fresh start in a much better environment.
A classic example from The Chronicles of Narnia, in The Lion, The Witch, and the Wardrobe, when Aslan returns, his presence alone is enough to end the hundred years of winter created by the White Witch, first bringing Christmas, then making flowers bloom and melting the frozen rivers without flooding. Within a day or so it has become early summer, restoring the natural balance. Characters that had been turned to stone by the Witch are revived by Aslan as well, though that takes more direct intervention.
Somewhat averted in the Left Behind book Kingdom Come, as God and Jesus spend a few months restoring the earth to its former beauty following the end of the Tribulation to make it new for the Millennial Kingdom.
The Great UnDoing in Septimus Heap works like this, and recovering its text is a major plot point in Darke.

Live Action TV

The Dakara Super weapon in Stargate SG 1 was originally designed to do this. Of course, given that it's called a "weapon"...
- More that it's a tool that can be used as a weapon. The protagonists just don't know the details about how it works or how to configure it (though when they used it, they did intend to use it as a weapon).
The wave of goodness caused by Zordon's death at the end of Power Rangers in Space which either killed or turned good all the villains from that point to the beginning of the franchise.
- Power Rangers Lost Galaxy end with the returned Sabers restores the people of Mirinoi. Even less understandably it revives the dead Pink Ranger (The character died because the actor was ill and the actor had recovered by the time of the finale)
Emma's good-bye kiss to Henry in the season ender of Once Upon a Time not only brings the kid back to life, but breaks the curse on the entire town of Storybrooke. Of course, so sooner had it happened than Rumplestitskin decided to trigger a spell which might invert the trope.

Video Games

De Blob's Transformation Engines send out a wave of positive energy that helps restore the color and plants of all the neighboring areas and gets rid of the gloomy gray sky.
At the end of The Legend of Zelda a Link To T He Past: Link makes a wish on the Triforce and undoes all of Ganon's evil actions, including bringing Link's Uncle and the King back to life.
- And in The Legend of Zelda the Wind Waker, Hyrule has been sealed away, and when you find it, everything is colorless. When you draw the Master Sword from it's pedestal, color sweeps slowly across the area, also reviving a bunch of tough enemies to test the Master Sword on.
- In The Legend of Zelda: The Minish Cap, once Vaati is defeated and Zelda wishes for everything to be back to normal, you see all the enemies vanishing from existance across Hyrule. Hyrule Castle is also repaired and returned to normal, and all the guards are turned back from being stone. It's even described as a 'miracle'.
The Golden Ending of Valkyrie Profile is in the form of this. Literal apocalypse was solved instantly.
In the 2008 Prince of Persia game, healing one of the fertile grounds results in a wave that wipes out the corrupted ruins revealing.... well, still ruins, but nice ruins overgrown with greenery.
Using the Bloom power on a Guardian Sapling in Okami results in a wave of flowers that removes the curse from the area.
At the end of Lunar 1, large parts of the world have had all life sucked from them and the main hero is gone, then this happens.
At the end of The Legend of Spyro Trilogy, Spyro uses his full power loose one to reverse the destruction of the world caused by the Destroyer. Though it seems to be a Heroic Sacrifice at first, it turns out he and Cynder both survive.
The AGD King's Quest III Fan Remake: If you are able to get a certain item, then it will create this effect over the dragon-ravaged Daventry at the end.
Your ultimate reward for reaching the center of the Galaxy in Spore is the Staff of Life, which allows you to create a wave of green energy that instantly transforms a barren planet into a thriving terraformed world. You can only use it 42 times, though.
In World of Warcraft, the re-origination device in Uldum is basically this - except that it doubles as a Reset Button. It purges all impurities and returns the world to a "virgin" state—hence getting rid of everyone, both good and bad. Needless to say for most mortals they believe the world isn't that far gone, so the struggle is keep it from going off.
Somewhat cynically used in Gears of War 3. The Imulsion was parasitic and the Lambent forces were merely an extension of that, most everything on the planet had some degree of contamination. Adam Fenix devised a pulse generating machine to neutralize the Lambent and in doing so it couldn't descriminate against the Imulsion in any living being, including Locust or Humans. Because the Locust had so much longer exposure to Imulsion they are virtually wiped out in the process. Humans who spent an inordinate amount of time with Imulsion were also killed, including Adam himself.
In Bastion, this is invoked but deconstructed in the Restoration ending. The Bastion completely resets the world, so the characters are replaced with their past selves, and there is nothing to stop events from repeating themselves.
In Super Robot Wars Z2: Saisei Hen, Uther does this in his strongest attack.
Stars! has "Genesis Device", technology for which cannot be researched, but only purchased from Mystery Traders. Upon building, it erases everything built on the planet's surface and resets all stats (environment and mineral concentrations) to random, just like for the planet generated anew. This does not guarantee the place will be valuable, or even habitable for its current owner - maybe it will improve the situation, or maybe you'll have to evacuate colonists and send in remote mining robots. When minerals are depleted and conditions are barely survivable even with terraforming, it's probably worth a shot, especially for more adaptable races. It takes time to build and requires high Tech Levels, i.e. becomes actually available only in very late game - but in very late game minerals are depleted and expansion grinds to stalemate, thus a chance at improving a low-value planet is more valuable too.
Ascendancy has "Lush Growth Bomb" project that can be produced on a planet "to make a planet surface significantly more habitable".

Western Animation

Code Lyoko: "Return to the past, now!" However, this comes with strings attached, and cannot reverse death or permanent virtualization.
Avatar: The Last Airbender: After the Fire Nation attacks, Aang brings up waters to put out the fires on the Earth kingdom. Not strictly a healing wave, but definitely in the spirit of it.
In Bionicle, Mata Nui does this to repair the fragmented world of Sphereus Magna. Effects include Terraforming, growing lage amounts of vegetation, and curing the effects of some Mutagenic Goo.
- The Staff of Artakha does this to repair all damage caused by the Great Cataclysm except for Karda Nui.
In the pilot of Rainbow Brite after the Evil One is destroyed the ground crumbles becoming Rainbow Land. In The Movie color and spring time is restored to Earth.
In ReBoot, the user restoring Mainframe has this effect.
After the match in Real Sumo Fighting 8 splits the world in half, the gyoji puts it back together.
In the Season 4 finale of Teen Titans Raven uses one of these to return the world to normal after Trigon turned all the people to stone, all the buildings into ruins, all the water into lava, and all the sky into a red haze. Since this happens the exact moment she defeats Trigon, it's unclear whether Raven personally created the wave of magical white light, or if banishing Trigon from the dimension automatically undid all the changes he made while there.
The Veggie Tales episode "Lord of the Beans" ends with the hero creating one of these with a magic bean thrown into a dry well.
Minor one in Generator Rex, when Six's previous mentor dies, his body changes into some kind of energy and causes vegetation life to grow.
In My Little Pony Friendship Is Magic "The Return Of Harmony Part 1", Twilight Sparkle tries to cancel out the bizare weather caused by Discord... it fails... miserably. When the Elements Of Harmony are unleashed on Discord, it not only turns him to stone but lets loose a World-Healing Wave that restores Equestria to how it was before Discord appeared.
At the end of Xiaolin Showdown's first season, Wuya's return to physical form causes the surrounding region to decay. When she is imprisoned in a puzzle box again near the beginning of the second season, a World-Healing Wave occures.