To be honest, life within the Marvel Cinematic Universe seems like a nightmare. It is constantly being interrupted by some potentially world-ending event. Sure, there are superheroes flying around to stop the bad guys, but their solutions are always to fist fight. This means that, at best, life is constantly being endangered by mega-powered beings dropping buildings on each other. That's not to mention all of the otherworldly threats. There are magical beings, outer space warlords and reality-altering events constantly endangering Earth. In the various Netflix series, characters are constantly referencing the time aliens invaded New York City. The thing is, while that was pretty bad, it's not uncommon for something like that to happen.
Even worse is how many times life was almost destroyed and nobody knew about it. Killmonger attempted to start a new world war by arming various groups with vibranium-powered weapons. While Black Panther and his allies were able to stop him, most people don't know how close they came to chaos. While situations like that are neatly wrapped up, that's not always the case. Sometimes, the villain's plan starts to come into focus, only for the heroes to stop them at the last moment. While this saves the world, there's still a huge mess that needs to be cleaned up. The infamous battle of New York left alien tech laying around all over the place, and as audiences saw in Spider-Man: Homecoming (2017), not all of it ended up in the right hands. There's always consequences, and these are the most cataclysmic disasters in the Marvel Cinematic Universe!
15 THE DESTRUCTION OF THE BIFROST
During the finale of Thor (2011), the titular hero finally learns to be selfless during his fight with Loki. The trickster turned on the Bifrost, opening a pathway to Jotunheim, home of the Asgardians enemies, the Frost Giants. Unfortunately, leaving the Bifrost open would destroy Jotunheim, and Loki had rendered the controls unreachable. Thor's only choice was to destroy the Bifrost, thus cutting him off from Jane Foster on Earth.
While this saved Jotunheim, it also cut off Asgard from the other realms. Fortunately, it was rebuilt within a few months. Within that time span, however, the realms fell into chaos. Considering that it only took Thor a few months to put everything back together, this catastrophe ended up not so bad.
14 XANDAR IS DECIMATED
In Guardians of the Galaxy (2014), Xandar, home of the Nova Corps, is established as one of the most powerful planets in the universe. After the Guardians successfully obtain the Power Stone and defeat Ronan, it makes sense for them to leave the powerful artifact with the Nova Corps.
At some point, Thanos attacks Xandar and steals the stone. It's never stated outright, but considering that Thanos has a habit of killing half the population of his conquests, things don't look good for Xandar. This sounds bad, but in all honesty, it apparently wasn't that big of a deal. The Guardians of the Galaxy didn't even know it happened, but it lead to Thanos killing half the universe so it's still pretty bad.
13 THE DARK DIMENSION ENGULFS EARTH
In Doctor Strange (2016), it's revealed that the Earth is protected from the Dark Dimension by three buildings known as Sanctums. A madman called Kaecilius contacts Dormammu, a powerful entity from the dimension, and helps coordinate an attack. After the London Sanctum is destroyed, Kaecilius is able to take down the Hong Kong Sanctum, weakening Earth's defenses enough for Dormammu to invade.
Luckily, Dr Strange used the Time Stone to run time backwards, allowing him, Mordo and Wong to prevent the Hong Kong Sanctum's destruction. Strange then uses the stone to bargain with Dormammu, sacrificing Kaecilius for Earth's safety. While this seems like a happy ending, Mordo ominously reveals that Strange broke the laws of nature, and the bill always comes due.
12 THE CONVERGENCE
Approximately every 5,000 years, the nine realms come into alignment. This event is called the Convergence, and it causes random portals between worlds to open up. Heimdall describes it as both incredibly dangerous and truly beautiful. An ancient enemy of Asgard, Malekith, hopes to use an item known as the Aether in combination with the Convergence to destroy the universe.
During Malekith's quest, Thor's mother Friga is killed. Even worse, Loki is able to fake his death, dispose of Odin and, disguised as his father, replace him on the throne. While Thor was able to prevent the destruction of all reality, the events of the Convergence led to both Ragnarok and Thanos' acquisition of the Infinity Stones.
11 RONAN'S ATTACK ON XANDAR
Xandar and the Kree Empire waged war against each other for hundreds of years before finally agreeing to a truce right before the events of Guardians of the Galaxy (2014). Unfortunately, not everyone was ready for peace. Ronan, a Kree soldier, agreed to help Thanos in return for the destruction of Xandar.
After coming into possession of the Power Stone, Ronan betrayed Thanos and launched an attack on Xandar. The Guardians prevented him from using the stone to wipe out all life on the planet, but the attack still caused heavy casualties among the Nova Corps. Considering that Xandar is soon wiped out by Thanos, this attack may have left them much weaker than anyone realized.
10 EGO'S SEEDS HATCH
In Guardians of the Galaxy Vol 2 (2017),Star-Lord met his father, Ego, an ancient Celestial being whose life essence had formed into a planet. Hoping to spread his essence across the universe, he formed a body and traveled from planet to planet, planting seeds of his life force.
He also impregnated countless women, hoping that the resulting child could help him control his energy while he hatched his seeds. Unfortunately, Ego's seeds were meant to consume and replace them with Ego. Also, he only needed a child to harness his energy, and had killed most of them. Star-Lord was forced to kill him, but only after each seed hatched and partially consumed their planets.
9 BATTLE OF HARLEM
One time, Bruce Banner visited New York City and he ended up breaking Harlem. While searching for a cure, he traveled to the Big Apple to meet with Dr Sterns. Banner was followed by General Ross' forces, which included Emil Blonsky. The soldier had been injected with a version of the super soldier serum and had gone partially insane.
After Banner was apprehended, Blonsky forced Sterns to enhance his blood with Banner's Hulk blood, turning himself into an Abomination. Ross' only option was to release the Hulk, who was eventually able to subdue Blonsky. Unfortunately, two giant monsters fist fighting each other didn't work out so well for anyone that owned property in the area.
8 THE MANDARIN ATTACKS
At the start of Iron Man 3 (2013), the United States has seemingly been targeted by a terrorist known as the Mandarin. Without any warning, mysterious explosions start rocking army bases around the world. It's only after each blast that the Mandarin releases a message, explaining why he chose the target. He often uses old American history to justify the violence.
It isn't until Happy Hogan is caught in a blast that Tony Stark starts to investigate. He discovers that the explosions aren't bombs, but actually accidents caused by experiments with the Extremis virus. It turns out, Aldrich Killian was responsible and the Mandarin was actually just a cover. Luckily, Tony blew up all of Killian's Extremis soldiers before they could cause any more damage.
7 THE ASSASSINATION OF T'CHAKA
During a mission in Lagos in Captain America: Civil War (2016), the Scarlet Witch accidentally redirects an explosion into a building. Unfortunately, humanitarian workers from the nation of Wakanda were caught in the blast and killed, kicking off an international incident. The U.N. called a meeting, where King T'Chaka was going to address the recent tragedy.
While T'Chaka was about to speak, he was killed by an assassin. This was all part of a plan by Helmut Zemo, who was seeking revenge against the Avengers. Zemo framed the Winter Soldier, knowing Captain America would come to his friend's rescue. This attack led to the splitting up of the Avengers, along with Killmonger's attempt to take the Wakandan throne.
6 THE FALL OF SHIELD
When Captain America woke up decades after being frozen, he joined S.H.I.E.L.D., a powerful security agency. Peggy Carter helped found the organization, so Cap trusted it. In Captain America: The Winter Soldier (2014), however, he discovered a massive conspiracy. It turns out, agents of Hydra infiltrated the spy organization from the beginning, and had been secretly running the show the entire time.
Their ultimate plan was to launch a trio of automated helicarriers that would target potential enemies of Hydra and kill them from the sky. While Cap stopped the launch, he also brought down all of S.H.I.E.L.D. with it. This caused all of the agency's secrets to be revealed to the public, which proved useful to several of the Avengers' enemies.
5 BATTLE OF SOKOVIA
When the AI program Ultron gained sentience, he quickly decided that he needed to wipe out humanity. He took inspiration from the extinction of the dinosaurs, and decided to artificially create an asteroid of his own. He did this by building a huge vibranium powered engine beneath the city of Sokovia. Then, he launched the city into the sky, with the intent of sending it crashing back down with enough force to wipe out all of humanity.
Fortunately, the Avengers were able to stop him. Unfortunately, they didn't arrive in time to stop the city from becoming airborne. The end result was the destruction of the entire city. There were plenty of people unhappy with this, and the Avengers spent years dealing with the aftermath.
4 KILLMONGER TAKES OVER WAKANDA
When Erik Killmonger revealed his existence to Wakanda, he was able to challenge the throne. As a relative to the previous king, he had the right to face T'Challa in hand-to-hand combat. After seemingly killing T'Challa, Killmonger took control of the nation. His plan was to send vibranium-powered weapons to his allies across the globe, with hopes that they would rise up against the established powers.
T'Challa survived, and was able to defeat Killmonger, stop the weapons, and reclaim the throne. Unfortunately, Killmonger did succeed in one aspect of his plan. He destroyed Wakanda's entire supply of the heart-shaped herb, which give the Black Panthers their power. What this means for future generations has yet to be seen.
3 THE BATTLE OF NEW YORK CITY
After the activation of the Tesseract and the arrival of Loki, Nick Fury realized that S.H.I.E.L.D. was outmatched. He called together the various heroes who had recently popped up, hoping they could come together to stop the threat. Initially, however, they didn't mix well and Loki was able to successfully open a portal to outer space above New York City and call forth the Chitauri army.
By this point, the heroes had worked out their differences and the Avengers were formed. While they won the battle, the city faced billions of dollars of damage. Not only that, but this put Earth in the crosshairs of Thanos, one of the galaxy's deadliest villains.
Asgard was always destined to fall. While Thor thought he could prevent it by killing Surtur and stealing his crown, he never had a chance. After Odin passed on, his firstborn daughter, Hela, returned from exile. The powerful goddess of death unleashed her fury on Asgard, crippling its army and raising one of her own.
She planned on conquering the cosmos, and was too powerful for Thor to stop. Since she drew her power from Asgard, his only choice was to initiate Ragnarok. While this saved the surviving Asgardians, it did weaken them and put them directly in the path of Thanos, who quickly decimated the former gods.
1 THANOS' SNAP
The worst event to occur in any movie, not just the Marvel movies, might be Thanos snapping his fingers. After the destruction of his home planet due to overpopulation, the mad Titan came up with a horrifying plan. He decided that there was too much life in the universe, and that half of it needed to die.
He achieved this by collecting the Infinity Stones. By combining all six, he became the most powerful entity in the known universe. Right as he collected the final stone, Thor appeared and buried his axe in the madman's chest. Unfortunately, he didn't go for a killing blow and Thanos was able to snap his fingers, causing half of all life to fade to dust.