Quentin Beck a.k.a Mysterio is a major antagonist of the Marvel Cinematic Universe, by appearing as the final antagonist of the Infinity Saga as the main antagonist of Spider-Man: Far From Home. He is a former Stark Industries illusions specialist who wants to become the world's biggest superhero in place of the late Tony Stark, feigning attacks from inter-dimensional beings called the Elementals to do so. A spiteful and emotionally unstable man, he ends up becoming the first real personal threat to Peter as his actions have, for the current moment, ruined the boy's life. He is the former friend turned archenemy of Spider-Man.
He is portrayed by Jake Gyllenhaal.
Spider-Man: Far From Home
Beck first appeared when "Nick Fury" and "Maria Hill" encountered Sandman, which he later destroys using his powers. Once Peter Parker and his friends get attacked by Hydro-Man in Venice, Beck saves Peter from its wrath. The two fight together and Beck destroys the Elemental, appearing as a hero to Italy. Later that night, Nick Fury brings Spider-Man to his hideout, where Spider-Man meets Beck. He unintentionally gave him his hero name Mysterio (something he was called by his classmates), a name which he liked.
Beck tells Spider-Man that he came from an Earth of a different dimension that was destroyed by the Elementals, and that they’re on the original Earth. He reveals that there are four of them and their elements: Earth, Water, Fire and Air. Fury suggested that Spider-Man team up with Mysterio to fight the last Elemental Molten Man, but Spider-Man refuses as he is too busy hanging with his classmates on their field trip.
Eventually, Spider-Man decides to leave his class' trip and help Mysterio fight Molten Man at the Prague Carnival. The two battle the Elemental for a long time, attacking it with their webs, lasers, and mists, along with surrounding rocks and water. However, they are unsuccessful in stopping the Elemental, as it absorbed enough metal to make itself unstoppable. Mysterio summons all his power and punches the giant in its chest, making it explode and dissipate forever.
After the defeat of Molten Man, Spider-Man and Mysterio head over to a bar, where Spider-Man confides in his relationship trouble and declares Mysterio worthy for a style Avenger. He then hands over his glasses (containing an intelligence system called E.D.I.T.H. built by Stark), saying that Mysterio should be worthy of being a great superhero just like Stark. However, after Spider-Man leaves, the bar is revealed to be an illusion, and Mysterio happily cheered for his team, (composed of former Stark Industries employees, mostly William Ginter Riva, Victoria Snow, Guterman, Janice Lincoln and Doug). It turns out that Beck himself was a former Stark Industries employee who created a projection prototype that Stark would later rename as B.A.R.F., and that Beck felt jealous and furious because of this event. Beck also commented that Stark fired him for his unstable behavior and that he actually plans to usurp Stark as the world's greatest hero, since the latter sacrificed himself to destroy Thanos and the Black Order. It also turns out that the Elementals are projection drones (built by Riva) as part of Mysterio's true plot to cement himself as a hero to the world and that he tricked Spider-Man into handing over E.D.I.T.H. to further facilitate his plans.
As Peter prepares to reveal his feelings for MJ, the two happen upon a piece of detritus and end up activating it, proving that Mysterio didn't notice that he accidentally bumped into one of his Drones and it lost a projector, which reveals that the Elementals are cybernetic beings and not magical monsters. They then realize that Beck is a fraud who was using them to make himself look like a hero to the public.
Around the same time, Mysterio realized the missing projector was orchestral in a rehearsal to his next battle, planning an Avengers-level threat. Knowing that his plan will be compromised, Mysterio later uses E.D.I.T.H. to find out that Spider-Man and MJ knew his true colors. He also prompts Giva that once he had to kill Spider-Man, Giva will get the blame. Once he gets to Berlin, Mysterio shoots 'Nick Fury' with one of his drones, then Spider-Man then encounters Mysterio, who fights against and torments him by making him go through separate illusions, such as Mysterio in full armor dropping MJ from the top of the Eiffel Tower, a dozen of mirrored Spider-Men attacking, a zombie Iron Man, a spider whose eyes form a marching army of Mysterios, and also trapping Spider-Man inside his helmet as a snow globe version of New York City including the Avengers Tower. He gets shot by Fury, which asks Peter who did he tell about his identity. Peter tells him that he only told Ned and MJ. Fury turns out to be a disguised Beck, who leads Peter in front of a speeding train.
Beck and his team unleash his largest illusion yet, Elemental Fusion in London, which is supposed to kill Michelle and the rest of Spider-Man's classmates. Then Spider-Man comes to the rescue and jumps into the Elemental Fusion's mouth and uses the Peter-Tingle to destroy the Drones inside of the Elemental. Mysterio with anger orders the Drones to attack Spider-Man.
After Spider-Man defeats the Drones, he confronts Mysterio to give him the E.D.I.T.H. glasses. Mysterio creates an illusion where Peter fights the remaining drones, using his Spider-Sense again. With Beck being shot by a drone, he attempts to give Peter the glasses but he turns out to be an illusion, as his real self attempts to shoot Spider-Man, but is stopped and shot by a drone through misfire. As Spider-Man watches as Mysterio succumbs to his wounds, he asked E.D.I.T.H. to confirm there were no active holograms in use within their vicinity, to ensure whether or not Beck was tricking him with another illusion. E.D.I.T.H. confirmed there are none, assuring Spider-Man that Mysterio is truly dead.
However, it turns out that Mysterio, knowing that his plan could fail and that he would die, had his crew edit the footage of him and Peter fighting the Elementals to frame Peter as the culprit behind the attacks and his death while revealing his true identity in revenge for foiling his plans. The footage is then given to and displayed by J. Jonah Jameson, exposing Peter's secret identity to the entire world and branding him as a menace to the world, much to Peter's distraught, as now the authorities are going to try to arrest him for crimes he never committed and all his loved ones are in danger from all those criminals he trapped as Spider-Man over the years while Mysterio goes down in history as one of the greatest superheroes who ever lived, fooling everyone into thinking Spider-Man is the enemy from beyond the grave.