There once was a time that the Marvel Cinematic Universe was thought to have a “villain problem” - but those notions have been left firmly in the past after the age of Killmonger, Hela, and Thanos. The bad folks of the MCU have become some of its strongest characters, and their individual arcs are sometimes more complete than the protagonists they’re battling - with a full origin, action climax, and demise often occurring within the course of a single film.
Traditionally, superheroes don’t vanquish their enemies - but the MCU’s mightiest heroes have frequently found cause to cross that ethical boundary and snuff out members of their rogues’ gallery for the greater good. Sometimes, these terminations are accidental and more often than not they’re the result of a villain’s own hubris - but almost all of them bring a satisfying conclusion to the story of a superhuman gone wrong. After all, it’s probably what they deserve.
What Happens: Thanos is just trying to make some soup for himself when the Avengers finally decide to live up to their name - tracking down the being that just wiped out half the life in the universe and taking him to task for his actions. Several of Earth’s Mightiest Heroes track the Mad Titan down to his retirement planet and aggressively accost him - with the Avengers holding Thanos down so Thor can chop the Infinity Gauntlet right off his arm. When Thanos doesn’t give them the answers they’re looking for, Thor finishes the job by lopping Thanos’s head off right then and there.
Why They Deserve It: Not only does Thanos eliminate trillions from existence, he also does away with the Infinity Stones so that the dusted cannot be brought back to life - at least, until Tony Stark invents time travel, that is. He definitely deserves to get axed, but the suddenness of his demise doesn’t make for a satisfying end to his villainous arc - fortunately, it isn’t quite the end of the Mad Titan.
What Happens: Ronan the Accuser falls due to his inability to comprehend the power of dance. Star-Lord’s pelvic sorcery distracts Ronan long enough that Rocket and Drax are able to reconstruct the Hadron Enforcer - which they use to disable his Universal Weapon and free the Power Stone. Peter Quill and then the rest of the Guardians grab on to the Stone and use its energy to dispatch Ronan from this mortal plane.
Why They Deserve It: Ronan was a zealot in every sense of the word. Despite a peace treaty between his people and Xandar, Ronan remained dedicated to snuffing out the home world of the Nova Corps - and he’s willing to commit terrible atrocities to get his revenge. For such a serious villain to get taken out in such a silly fashion is highly satisfying - and tonally perfect for a Guardians film.
What Happens: Avengers: Age of Ultron does not end well for its titular villain. His attempt to escape Sokovia in a stolen Quinjet is foiled by the Hulk, and then Ultron has his mechanical heart literally ripped from his chest by a vengeful Scarlet Witch. The destruction of Sokovia leaves only a single Ultron sentry intact, but when the villainous AI tries to sneak away he is stopped and ended - by his own “son,” Vision.
Why They Deserve It: Ultron is in the midst of an attempt to eliminate most life on the planet when the Avengers defeat him, so it’s tough to argue that he didn’t have it coming. He also ends an Avenger - Quicksilver - on his very first day as one of Earth’s Mightiest Heroes. That the threat of Ultron was eliminated by his own creation adds an extra layer of satisfying irony to this demise.
What Happens: The end of Ego the Living Planet is a true group effort. Baby Groot deposits an incendiary device in Ego’s “brain” while the rest of the Guardians do battle with his monstrous planetary form. The fight ultimately comes down to Ego versus Peter Quill in an all-out celestial brawl that manages to distract Ego long enough for the device to crumble him to dust.
Why They Deserve It: Ego is able to convince audiences - and his son - that he deserves a painful end with one line of dialogue. When he admits to having implanted a tumor in Meredith Quill’s head, it puts him into firm conflict with his progeny. There’s also his plot to overwrite all life in the universe, but really that’s just bonus justification - Ego seals his fate when he ends Star-Lord’s mom and squishes his Walkman.