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Given that this would be a darker movie than the usual MCU film, practically everyone in the main cast barring the Children of Thanos and Secretary Ross have fallen under this trope. By the climax, you can more or less assume that someone in the main cast has died by Thanos's hands, been forced to watch as their loved ones get killed, or died shortly after being forced to watched their loved ones get killed.
- Wanda Maximoff in particular could be the biggest of them all. Continuing her long Trauma Conga Line from Avengers: Age of Ultron and Captain America: Civil War, her chance of having a normal life with Vision comes to an end when the Children of Thanos attacks them and nearly kills them both. Then, in order to prevent Thanos from getting the Mind Stone, she was forced to destroy it along with Vision. Then to rub salt to the wound, Thanos undoes Vision's sacrifice only to brutally kill him again in front of her. And not long after that, she gets erased from existence by Thanos's Badass Fingersnap.
- Coming in a close second is Thor who, after going through hell in his last movie, has his people's ship attacked by Thanos. This leads to his brother, best friend (Heimdall), and half of his remaining people being killed. Then after nearly getting himself killed in hopes of getting a weapon that could kill Thanos and save everyone else, he lands a blow that only wounds the villain and gives him the opportunity to finish his plan. As a result, his failure indirectly enables half of the universe's population being erased from existence. And while this is more minor, something to keep in mind is he's still not aware of how the Avengers became of a hollow shell of their former selves at the end of Civil War, and learning that his friends and comrades are no longer on speaking terms in the sequel is almost certainly going to do nothing to lift his spirits.Thor: Well, if I'm wrong, what more could I lose?
- Tony is a big one too. Ever since the first Avengers movie he has been suffering through fear of the coming Thanos threat and have been trying every precaution to stop him from destroying everything he loves. His attempts to prepare for Thanos only end up making the situation worse for the world, and ends up alienating himself from most of his teammates. Not only does he fail to stop Thanos by the end of the film like the rest of the heroes but he personally gets to see the rest of the heroes who went with him to Titan disintegrate, including Peter Parker who he mentored and looked up to him.
- Steve also jumps on the Woobie train as well. All his efforts to protect Vision and the Mind Stone from Thanos results in an All for Nothing, and he witnesses Bucky erased from existence, meaning he's forced to watch as his best friend and the only reminder of his past life die a second time. Unlike the first time, however, he's really dead. To make matters worse, his other best friend Sam is also erased from existence soon afterwards.
- Rocket, big time. After he spent the last movie pushing his newfound friends away until Yondu called him out on it, he acknowledges in this movie that he has a lot to lose. At the end of the movie, he is not only the last Guardian left (if you don't count Nebula), he is also forced to watch Groot dying a second time.
- For all the flak Peter Quill got for beating Thanos up just as everyone else got the Infinity Gauntlet off, he has just learned that Thanos killed Gamora and the last thing they said to each other was a love confession. And considering that he has lost his mother, his father and father figure before this, it's a wonder how Peter holds up till the end. And moments before he gets erased, the expression on his face shows that he clearly knows that he screwed up, all the while watching helplessly as his teammates/second family get erased one by one.
- Nebula is also very sympathetic here, as we finally get to witness just how horribly she is treated by Thanos, as she is constantly tortured by him in the most excruciating and painful way possible so that Gamora will be forced to reveal exactly where the Soul Stone is. To make matters worse, after finally being able to bond with Gamora in their last film, she had realized that she got killed off by Thanos in order to retrieve the said stone. She even once asks Thanos why didn't he just kill her to end her torment, and Thanos cold-heartedly replies it was because "it would be a waste of parts". Not to mention that she clearly showed legitimate guilt that her trying to stop Thanos led to the death of her sister whom she finally bonded with, along with the trillions of innocents across the universe — tragically including all of her new teammates sans Tony, as she witnesses each of them get vanished one by one.
- Gamora also falls into this as well. She begins to start a love relationship with Quill, only to get taken away by Thanos to realize that he eliminated half of her kind and took her from her home planet. Worse, she got to witness her adoptive sister, Nebula, be brutally tortured by Thanos in order to make Gamora tell Thanos where exactly the Soul Stone is. When Red Skull makes it clear that she needs to be sacrificed in order for Thanos to retrieve the said stone, Gamora tries to kill herself in order to prevent the stone from coming to Thanos, which will eventually result in trillions across the universe dying. However, Thanos stops her from doing so and, without the support from her friends during her final moments, gets helplessly thrown to her heartbreaking death.
- Peter Parker, full-stop. His death scene, as he sobs in fear that he doesn't want to die before falling limp into Tony Stark's arms and disintegrating, is regarded as one of the saddest moments in the entire MCU.
- Bucky Barnes, after a complete recovery from Hydra in Wakanda, has to go into war once again, and is the first person shown to decimate in Thanos' snap- even calling out to Steve right before completely turning to dust.