Despite the controversy around it, there’s a big reason Quicksilver’s death in Ultron program morphs into a murderous A.I. villain set on wiping out humanity. To ultimately defeat Ultron, the Avengers team up with two new heroes, siblings Wanda (Elizabeth Olsen) and Pietro Maximoff (Aaron Taylor-Johnson).
Originally teased in a post-credits scene in Captain America: The Winter Soldier, the Maximoff twins are survivors of HYDRA’s experiments with Loki’s Scepter. The Mind Stone in the scepter helped unlock abilities in the twins, turning Wanda into the powerful soreress Scarlet Witch and Pietro into superhuman speedster Quicksilver. Though the pair get off to a rough start with the Avengers, they eventually help the heroes take down Ultron. In doing so, Pietro, somewhat controversially, loses his life.
Quicksilver's death in Age of Ultron was shocking, but it needed to happen. In the film, Ultron lifts the capital city of fictional European country Sokovia into the air, attempting to bring it down like a meteor and create a mass extinction event. The Avengers are working to evacuate the city when Ultron attacks them with a fighter jet. Hawkeye and a little boy are right in the line of fire until Quicksilver shows up to save them, moving inhumanly fast to hustle them out of harm's way. Unfortunately, Pietro takes Ultron's bullets instead, bringing on the rage of Marvel fans who thought the speedster should've lived.
Though he wasn’t around for long, Quicksilver’s demise brought real stakes to the Marvel Cinematic Universe. With his death, Marvel showed that superhuman abilities and a moral com aren’t always enough to keep characters safe (while, granted, also keeping their main roster of characters intact). From WandaVision.
While Quicksilver’s death in Avengers: Age of Ultron was necessary, it doesn’t mean fans need to be happy about it. The circumstances of Pietro’s death are, objectively, ridiculous. While the Avengers are ushering citizens to safety from a floating city, Ultron, a highly intelligent and resilient robot with any number of yet-unseen abilities, decides to shoot at the heroes from a jet. Also, an earlier scene in the film showed that bullets move incredibly slowly from Pietro's perspective. He should’ve had plenty of time to redirect the bullets or simply move out of the way. Instead, he let them all go through his body. It’s a pretty terrible plan from Pietro, but overall the death benefits Marvel.
