The Last Stand. In my universe, the Evolutions along with there OP leader fought against the military from 20 different countries, all of them pretty large, and won. Millions died, and the death count was higher than the one of World War 2. It almost quadrupled the death count of WW1 and WW2 combined. This basically sealed Humanity´s fate of trying to live in the back corners of the earth as the Evolution´s prospered, and being food for their OP leader.
The Deadliest moment in mine was called Dragon Descent. This is loosely based on D&D. It was when the Ancient Chromatic Dragons attacked to Phoenix Continent which killed a vast majority of the races. The only reason why anyone survived, and why it ended, is because the most powerful Ancient Golden Dragon persuaded the other Ancient Metallic Dragons to fight for the lower races.
The deadliest event happens at the end when the daughter of the story's protagonist gets possessed by her real father, a god, and causes an earthquake so catastrophic that about a third of the population gets wiped out.
Sounds brutal. My world doesn't have many natural disasters on account of being a living thing. However, magical accidents have killed many in the past. This actually lead to the founding of a country dedicated to science and completely opposed to the practice of magic. It is actually a city-state called Veiled and it hid itself a long time ago to do its own thing undisturbed. Thus both sword-sorcery fantasy and science-fiction exist in my world but keep themselves separated by choice. (Until an evil villain tries to merge science and magic into a single discipline with the major benefits of both while cutting down the drawbacks. His experiments to achieve this resulted in many horrible atrocities inflicted on inmates in his care as a prison warden.)
The Subject Becoming. Basically, humans were trying to invent a serum that would allow superhuman soldiers to exist, so they created a campaign where the test subjects would sign up for the testing, thinking it was psychological testing, when they were drugged and strapped to the table and had the test serum injected into them. They usually died after 10 seconds, in slow and painful ways.
However, the last subject to ever BE tested actually didn't die, but was transformed from the inside (VERY PAINFULLY) out into something non-human, and ended up killing a shit-ton of people (A total of 3-4ths the world population) before another force took over the world and she was forced into hiding in ¨Dead Zones" where he has no control because the virus got out of hand so he couldn't control anything there.
The deadliest event in my universes history would be the fall of Asgard, a city the size of a small galaxy that is almost completely inhabited by a race called the divines. The city was destroyed by Siege, a resurrected villain from earlier in the story. Despite how densely populated Asgard was, only a couple hundred divines survived. This isn't even counting the casualties of Earth's and Siege's forces.
The deadliest even in my story is the War of the Beasts. Beasts of unimaginable size, power and numbers invaded from Dark Side (it's out of the world, and Dark doesn't necessarily evil). Pretty everything built was destroyed. About 90% of Herentei (humans) and 70% of Kíenarei (immortals) were killed. The Seven Beings (gods) who had been silently observing since the Creation had to intervene and seven pregnant Kíenarei gave birth to children of pretty much unimaginable power (there were 8 kids though, one had twins). These were the first Ketyrei (elves), but the later elves were a lot less powerful. They had to enclose an area with a "wall" that magical energies can't pass through with all the Beasts in it. Most of them died immediately as they can't live without magical energies. The ones that survived are the dinosaurs, and were considered small by their standards. The area blocked off was this world.
The worst disaster in my world actually occurred right after (a few hours) what the galaxy assumed to be the worst war in history; the First Galactic War. After the starter of the war surrendered (which no one really trusted, but they were taken far away to a prison located on a cold, ocean like moon in a neighboring solar system to Sol (Earth's system is named Sol in this world) and they were interrogated. While they spoke 90% nonsense, which leaded to everyone believing that their mind had deteriorated greatly in the passing years; they mentioned a weapon built around a massive star. When questioned further, it was revealed they planned to create an impenetrable station that would basically lock onto different stars, surround them, and slowly suck the star from existence. The plan was to go from star to star, taking away the light in the solar systems, leaving everyone into a cold death, while using the star as fuel to move the station around.
But since they surrendered, the station was left unattended, and thus the inner shield of the station was slowly breaking without management. Then they laughed about a disaster, and that was all they gave up about information. In a desperate attempt to disable the station, many races sent ships to investigate, but that was sending them to their deaths instead. The station shield fell, and the star within, still at large made the machinery within go crazy. While only two ships made it to the jump out of there, 25 ships and 7500 men and women perished at the first line when there was a bright explosion, seen from many light years away. The resulting damage was due to the unlucky planets and moons close to the explosions, which had their atmosphere ripped apart, and the surface boiled and roasted.
That adds about 2 billion to the deathcount.
A rouge planet, named Clariz, had a colony of creatures who are unable to survive with too much sunlight, thus making the rogue perfect. Unknowingly, the planet was alive; a creature never seen before was awakened by the explosions, and Clariz awoke right away, knowing immediately about the uninvited guests on its surface. The planet wiped them all out, adding 7 million more deaths.
Even though the force of the explosion gradually weakened, it assisted in blackouts on different planets, resulting in a few million deaths for those that required machines to survive. This has to be the greatest disaster in my world, and it was caused by a former earthling, not quite human; who began to suffer from insanity in their final years, leaving quite a mark on the galaxy.
In actuality, the most deadly event would be the creation of Chess and its expansion into Card, Cross, Capitol, and eventually, it's creation of the country of Chance.
The most deadly event in my universe is when a race in another dimension decided they didn’t like any other aliens so they decided to genocide all other sentient species in their galaxy
Let's see… two events.
The Rift: where a space-time sword created a separate alternate version of this world I have, which was then laid over the top of this planet, staked into place by the planets ley nodes (where magic flows through), and most demura and halois (two of the three races on this planet, along with humans) were sent there as a means of protection, when in reality this new dimension is an extremely terrifying place, and is taken over by a ruthless king, who kills most of the halois. This causes an incredibly unstable planet and there are occasional holes that appear between the two and either someone is deposited back on the planet, or sucked through into this dark dimension. Any humans or halois are killed by this king.
The second is when the main characters mistakenly create a post-apocalyptic world when they thought they were saving it. It causes the death of hundreds of thousands, and completely terraforms the planet.
The most deadly event in my world was the Great Wyvern War.
Basically, humans were overhunting wyverns so they could build weapons, armor, buildings, et cetera because of how strong they were. The wyverns didn't like this, so they banded together to do pretty much the same thing a la the Fatalis from Monster Hunter, rounding up and melting down humans to coat their scales (which is as gross as it sounds). The dragons didn't enjoy this kind of genocide one bit, and the humans who were fighting began to really start attacking wyverns. Both humans and wyverns told the dragons to keep their snouts out of this, and my main character is a Half-Dragon (human mother, dragon father) who is living in secret with his family. Rather than split the family to take sides, they decided to create their own side and gather all of the magic users in the world.
Benders and Animus users began to join forces despite the fact that magic is extremely rare and illegal on every continent, and they decided to point their extremely powerful magics at every side in hopes to get them to stop for, like, five seconds so they could talk things out. Benders function like more powerful versions of the ones from The Last Airbender, and are mostly dragons or draconic spawn. Animus can mess with the laws of the universe by simply enchanting something, and are either dragons, draconic spawn, or humans. Of course, some blowhard general is going to attack them and get their ass kicked, and this display of power is going to change the political structure of the world for a long time. Poor wyverns just wanted to live, for crying out loud!
There was a massive worldwide pandemic that happened as a result from extreme poullution in the water supply. 90 percent of the population, and the ten Guardians died trying to save the 10 percent of survivors. They renewed the world, but were never seen from again.
Um Hey, I'm new here. So the worst thing that happened in my story was a war between the god of Chaos and the other gods that destroyed everyone who fought in it over a 1000 years ago.
The deadliest war in my universe is kinda convuluted but basically boils down to a man who has godlike telekenesis and mind control snaps after being betrayed again and again, turns on the world he loves, and kills the better part of it. Somehow, he misses one.
Hmm…
Morlus kills almost all the Elementalists.
Soáki makes the San Francisco earthquake.
Addar destroys an army that spans across an entire galaxy.
Im probably being the annoying one who gets into the concersation but…
The seer crhonicles: the mage genocide caused by lots of angry people afraid of magic.
Unnamed sci-fy universe: basically a whole race got almost extinc because a bunch of volcanoes exploted.
Project failure (gonna work on that later): a whole civilization dissapeared for unknow reasons.
You should call the last ones the Ronok. (Like the Roanoke Colony.)
Probably the war on the soil of a human country named Tray, where the dragons, their enemies, started burning as much land as they could when the queen leading the draconic invasion died and left a brief but devastating power vacumn. Without that very important central command, the draconic armies just sort of fell apart and they began losing, badly. Many soldiers realized that and decided they were going to cause as much damage as possible before they get chased away or struck down.
The most devastating event in my world was probably the 'outbreak'. When the world was still being explored, a band of explorers found a dark cavern filled with several precious and rare gems, and an unknown species of fungi. Deciding to document the cave, they brought back samples of the gems and the fungi. What they didn't realise is that the fungi they brought back would cause an outbreak that would cause the death of a quarter of the population. Symptoms in the first stage include, headaches, fever, nausea, and sometimes vomiting. This stage is when person's immune system is trying to fight off the fungi. The next stage is when the fungi has taken hold of person. This is when the patient becomes unable to tolerate light sources, squinting or shielding their eyes, they will have an altered mental state, symptoms of disorientation, confusion, a lack of alertness or judgment of thought, hearing difficulty, and minor memory loss (unable to recognise faces, names, unable to judge time correctly). In the next stage the person will lose control of their body, actively seeking out dark and humid areas, having lapses where they become unresponsive and almost vegetative. By this point, the fungi will have spread to the brain and internal organs and the person will die from their lungs collapsing. The last stage occurs after the person's death, the fungi will erupt out of any openings in the person (the mouth, eyes, nose, ears, any deep cuts), and release its spores. The fungi is not contagious until this final stage, when the spores spread to other people through the air. This type of disease had never been seen before, so it took them a while to understand how it spread, but by the time they understood it, too many people had been infected. Once the outbreak had finally been contained, laws surrounding agriculture and exploring new places became incredibly strict, and people even remotely suspected of being infected were quarantined and isolated from the rest of society. The Outbreak is something that happened hundreds of years ago, but it still effects the society to this day, with memorials still being held and the history and safety precautions still being taught to young children through cautionary folk tales and stories.
A giant, glowing meteor hit the Earth in 2700 B.C., bringing monsters and super-powered humans in their wake. Almost half of the population of humans then either died from the meteor strike or gain superpowers/mutations.