All spoilers on this page are left unmarked. You Have Been Warned!
Serving as the Grand Finale of the original Myth Arc of the Marvel Cinematic Universe, it's perhaps fitting that Endgame has a far greater dose of horrors than previous films in the franchise. Retaining the darker tone and violence of its predecessor as well as genuinely terrifying scenes of its own that easily could have bumped the film up to an R rating, the end of the Infinity Saga will keep you awake at night (at least when you aren't crying your eyes out).
- The beginning of the film takes place during the Decimation in Clint's POV. He's just spending an ordinary day with his wife and children when they suddenly disappear without explanation while he isn't looking. What really hits it home is that we see wisps of dust billowing away, but it's such a minuscule amount that it's only because we know what happened in the previous film that we recognize it. To those without that knowledge, like Clint, it's a literal Blink-and-You-Miss-It; his family disappeared without a trace.
- The film also shows what places like NYC and San Francisco look like after the Decimation: Completely lifeless. The weather is murky and dark, showing how low the atmosphere has fallen with only half of life on Earth. Keep in mind that Thanos wanted to erase half of life in the universe to have resources last and reduce the risk of the Overpopulation Crisis that befell his home planet Titan. And this is the end result: Earth didn't thrive; it is utterly silenced and visibly rotting.
- The psychological damage done to humanity is arguably even worse. Every human being has been deeply, irrevocably scarred. Everyone has lost people they love (half the people they love, in fact), and it's likely they watched as those people turned to dust in front of them. No explanation, no help coming, no hope of return. It's amazing that society didn't collapse overnight as 3.5 billion humans went insane with rage and grief. Which is implied to be a real issue, considering there are therapy sessions set up to help people come to terms with The Snap. It will take generations for the world to get over the damage done to its collective psyche. Perhaps best exemplified when Scott asks a passing kid what happened...and the barely-teenaged boy just gives him a cold, dead Thousand-Yard Stare, before riding away.
- The confrontation with Thanos in the Garden features some graphic violence and Body Horror that would not be out of place in an R-rated film.
- Thor actually does make good on his previous failure. Violently. What makes it scary is the buildup: Thor crashes straight into Thanos' hut and immediately severs his arm, causing Thanos to scream even louder than when Stormbreaker was shoved into his chest. When Thanos is restrained by the other Avengers, he congratulates Nebula on noticing his honesty and even regrets his abusive treatment of her. Thor stands silently hearing Thanos' spiel about the Stones' destruction. Then, all of a sudden, the familiar sound of Stormbreaker activating, with its blade glowing blue and Thor's cry of rage, are all signs that warn viewers of Thanos' quick end as Thor, in absolute rage, slices Thanos's head clean off.Thor: ...I went for the head.
- The shocking amount of Gorn there is in the scene, putting aside the aforementioned burns on Thanos' body. When Thor slices off his arm, for about a split second it shows the exact moment he chops it off, leaving behind a burnt stump that seems to be caked in his Alien Blood; if Thor had dismembered him just a bit slower, it could have easily led to the Titan bleeding out. And then, when Thor finally decapitates Thanos, in the midst of a burst of his blood, his jugular vein can be seen hanging from his neck, and a portion of his spinal cord visible from the bottom of his head, also for a second only.
- Past Thanos viewing the same scene in Nebula's memories actually shows the cut where Thanos' head was for a split second, though it's being seen through a hologram that partially censors it.
- Thanos himself doesn't even flinch at what is basically his own recorded death, making you wonder what deep shades of hell made him so cynical that he isn't disturbed by such.
- Before the Avengers actually manage to find Thanos at the Garden, they spend the entire time looking for him via any means possible. Steve even presses Tony for any clues Thanos may have given him during their fight. If you think about it from the remaining Avengers' perspective (with the exception of Tony's because he absolutely wants nothing to do with Thanos anymore after nearly getting killed), the mere thought of a near-omnipotent madman just roaming around doing God-knows-what somewhere in the universe is frightening enough that they are willing to instantly jump at any info about Thanos' whereabouts. Even worse is the possibility of Thanos coming back to Earth with his entire army brought back using the Infinity Gauntlet and deciding to finish the job. Even with Captain Marvel on their side, the Avengers know that they lack too much manpower to mount a proper defense so they decide to ambush Thanos. This conversation between Natasha and Steve sums up the desperation everyone feels as they go to what they felt was a Suicide Mission:Natasha: [Ambushing Thanos] is going to work, Steve.
Steve: I know it will... because I don't know what I will do if it doesn't.
- Even given who the target was and what he had just accomplished, the whole assault against Thanos and his death is as brutal as it is cathartic. Once they find Thanos (albeit weaker than before), the Avengers sent there for the ambush proceed to effectively crush him in just a few minutes, highlighted by the fact that Thanos didn't try to throw a punch back. It really cemented that the remaining Avengers had practically nothing else to lose by that point and were willing to do anything to at least get something out of their loss, if not save everybody that Thanos snapped. Rhodey especially hits it home with his suggestion of killing Thanos as a baby when they figure out time travel (although Bruce's reactions to that suggestion helped frame it in a comically dark context).
- Thor actually does make good on his previous failure. Violently. What makes it scary is the buildup: Thor crashes straight into Thanos' hut and immediately severs his arm, causing Thanos to scream even louder than when Stormbreaker was shoved into his chest. When Thanos is restrained by the other Avengers, he congratulates Nebula on noticing his honesty and even regrets his abusive treatment of her. Thor stands silently hearing Thanos' spiel about the Stones' destruction. Then, all of a sudden, the familiar sound of Stormbreaker activating, with its blade glowing blue and Thor's cry of rage, are all signs that warn viewers of Thanos' quick end as Thor, in absolute rage, slices Thanos's head clean off.
- Think about Scott Lang for a moment. He gets pulled out of the Quantum Realm by a rat randomly hitting the button needed to pull him back. From his perception, he was gone for only five hours. When he gets back, he learns that five years have passed...and the world has lost half its population, including the Pyms and the Wombats. Scott Lang finds himself in a Bad Future that few can dream of. The fact that he didn't fall into a Heroic BSoD from sheer horror is phenomenal.
- He finds a memorial to "The Vanished" and frantically searches it while uttering a Rapid-Fire "No!", hoping to not see Cassie's name. Her name isn't there, but another one is: His own. His little girl thinks her father, her hero, has been dead for five years... and Scott has missed five years of his beloved daughter's life.
- Cassie and Scott are both visibly shaken when they see each other again. It takes him a while to realize this strange teenage girl is Cassie, and she's doubting her eyes as she tries to fathom how her father's return is even possible. Look at her body language; you get the sense she's expecting this to be some cruel trick. It's basically a fulfillment of Hope's Adult Fear moment in Ant-Man and the Wasp; after all this time, would a parent and child even recognize each other?
- Everything about Nebula's terrible experience in the past. While everyone else save Clint and Natasha get adventures in the past that are either lighthearted, fun, or heartwarming in some way or another, Nebula's takes a deep turn into misery when Thanos finds out what the Avengers are up to. It says a lot that Nebula, usually unflappable and emotionless, reacts with unbridled terror upon realizing that he's cottoning on. We once again see how he treats his so-called children: He tortures Past Nebula in order to figure out what appears to be nothing but a simple glitch. And her own past self, desperate for her father's recognition, brutalizes and nearly kills her in turn...and can't even break free even when it's clear on some level she wants to. As Nebula isn't one of the primary Avengers, the whole sequence comes with the very real fear that she's about to be killed at any moment, especially when Thanos decides to do what was very nearly a Kill and Replace to sabotage the Avengers' efforts.
- The Book-Ends of the segment really sell it. Nebula begins it by desperately trying to warn Clint and Natasha that Thanos is aware of what's going on, but fails. It ends with her captured and her psychopathic past self heading to the future in her stead with her unable to do anything but beg Past Gamora to stop it from happening.
- Think about the Battle of New York in the new timeline, from the point of view of the original Avengers of that period. The battle is won, Loki is in custody, and the Tesseract and the Scepter are being taken away. Then, suddenly, Tony has a heart attack and, in the confusion, Loki grabs the Tesseract and teleports away while, as far as they can tell, someone who may be Loki or an unknown third party impersonates Captain America and tricks S.H.I.E.L.D. into giving him the Scepter. Also keep in mind Loki's objective was to get the Tesseract to Thanos and he's probably going to go deliver it now, and the HYDRA agents inside S.H.I.E.L.D. briefly think Steve Rogers has joined them (though in after-action reports, they'll probably deduce it was Loki). Whatever is going to happen in the future of this timeline, it can't be good.
- The heart attack becomes worse when you remember that Tony already had a near-death experience just about an hour ago. The others might be worried if it's a side effect of whatever happened to him in space.
- The time for Scott and Tony between when Loki teleports and Tony figures out another time to take the Tesseract must have been a nightmare. Everything up to this moment said everyone had one shot at this and they missed. Even worse, Tony — the one who took the responsibility of protecting the Earth from Thanos the most personally — has now failed in what is most likely their last chance. Its a worst case scenario made real.
- Remember wincing at seeing Gamora's corpse at the bottom of Vormir after Thanos sacrifices her for the Soul Stone during Infinity War? Now you get to see that all over again...but with longtime Avenger Natasha/Black Widow instead. That also comes with the bonus of the blood spatter on the rocks around Natasha's head not being Alien Blood as it was with Gamora. All of this after seeing Natasha and Clint effectively having a skirmish of who would sacrifice themselves first so the other could leave with the stone.
- Natasha's death also serves as a explicit confirmation about what is easily the most harrowing things about the Soul Stone: a sacrifice for the stone is a permanent exchange. Anyone whose soul is given up for the stone cannot be brought back, even with all of the Infinity Stones in tow. Banner intones with regret near the end of the film that when he used the stones to revive everyone Thanos erased, he tried bringing Natasha back as well, but to no avail. By the same token, the Gamora that now exists in the prime timeline is a different Gamora from the past that does not know any of the Guardians. The Gamora that previously existed in this timeline and was sacrificed by Thanos for the Soul Stone is still dead, and it's only through Past Thanos taking Past Gamora with him into the present that any Gamora exists in this timeline at all.
- The full extent of the damage that the Infinity Stones exert on its wearer, when used all at once, is shown. The initial surge of radiation upon the Stones ingratiating with the wielder causes Hulk to double over in pain. He survives activating due to the radiation already in his body, though it costs him the use of his hand; even at the end of the movie, his arm is shown in a sling, indicating that the damage caused might be permanent. Tony's use of it, while being a normal human, is what causes his death: After donning it, he only has enough strength to speak his Pre-Mortem One-Liner, while after activating it, he dies where he stands, with his final words being a barely-audible "Hey, Pep."
- As Tony wields the Stones, you can actually see the energies tearing through his armor. After his snap, his body is so badly damaged, his ear has burned off. And Tony, one of the most notorious Motor Mouths in movie history, can't even speak to Rhodey or Peter when the two discover his damaged state.
- Thanos' Two-Face appearance as mentioned above. His final appearance is made all the more damning in that unlike the two human Avengers utilizing a high-tech gauntlet solution, he was a Titan with a gauntlet specifically forged to handle the use of the stones.
- The Mood Whiplash after the successful snap back. Clint gets a call from his wife, Scott admires some birds seemingly returned in one of the compound's gardens and happily states that their plan worked...and then a wounded Bruce looks up and sees the shadow of the Sanctuary II opening fire...
- In the immediate aftermath of Thanos' bombardment of the compound, the explosion has trapped Banner (who's effectively down an arm due to using the Gauntlet), Rhodey (who is paraplegic and now stripped of his mechanical leg braces), and Rocket (who, despite his enhancements, is still a raccoon and physically pretty weak) under tons of rubble as water from the river pours in. For anyone suffering from claustrophobia and/or hydrophobia, it's a terrifying sequence. Rocket, in particular, is freaking out. He eventually reaches the point where he just stops talking and starts to cry out, sounding like a terrified animal or kid, which is made even worse by the fact that Rocket almost never shows fear like this.
- Immediately after this, Clint has been knocked somewhere into the ruined bowels of the Avengers' base along with the Infinity Gauntlet. He seems fine, picks up the Gauntlet, and prepares to find a way out. Then, he hears a quiet growl, so he fires a light arrow at the darkness behind him, which reveals a pack of Thanos' Outriders charging him, out for blood. The cramped setting, red lighting, and snarling monsters evokes images of Aliens as well as the scares that movie brought.
- The Russo Brothers revealed that they had originally planned on having 2014 Thanos go to his timeline's Earth, kill all the humans there, along with the Avengers, and then come to the present with 2014 Captain Americas severed head. Its probably best that it wasnt included, as it would have been horribly gruesome to see Caps decapitated head.
I am... ineditable.