The Nietzscheans of Andromeda brought about the fall of the multiple galaxy-spanning Commonwealth. Their precise motivations aren't so clear. In a twist, it becomes clear fairly early on that Neitzscheans aren't so superior physical or mentally to the average human, in part because most of humanity is genetically modified in some way or the other. One should beware the superman, but more because he thinks he is a superman than because he is one. According to the background material, the Nietzscheans had legitimate concerns, especially after the Magog invasion and the resultant treaty, which gave the Magog a number of border worlds, most of which were settled by Nietzscheans. To these übermenschen, this was not only a betrayal of them by the Commonwealth but appeasement (see World War II for how well that worked historically). Their goal was to replace the "weak" government with a powerful Nietzschean Empire with the Drago-Kazov pride as the imperial dynasty. Thanks to Dylan, that was not meant to be, although it's implied that the empire would've quickly collapsed on itself through infighting, given their tendency toward Chronic Backstabbing Disorder.
In Supergirl (2015), exposure to Red Kryptonite makes Kara into a berserk Person of Mass Destruction, attacking people and destroying everything in her way. She's overcome with remorse when the effects wear off, as the people of National City now fear her.
The Crisis on Earth-X crossover features an alternate reality where the Nazis took over the world and heroes like Green Arrow, Supergirl and the Flash are Nazis as well. The Dark Arrow in particular serves as the current Fuhrer during the start of the event.
This is one of the main themes of The Boys (2019). Superheroes, just like normal human characters in this world, are at best individuals dealing with serious issues and at worst are villains Drunk with Power.
Homelander: Go ahead. Release it. Let's light this candle, huh? I mean, sure, I'll lose everything, but then... I'll have nothing to lose. First, I'll take out the nerve centers — White House, Pentagon — then any domestic defense capabilities, and then critical infrastructure — like cellular, Internet, that kind of thing... and then... well, I think then... I'll just wipe New York off the fuckin' map.For fun! I'll even throw in Des Moines and that little cousin-fucker hick town that Maeve's from, cause why not? See, Starlight, I'd prefer to be loved. I would, but if you take that away from me... Well. Being feared is A-one okey-doke by me. So. Go ahead, partner. Do it.[Beat] No? You don't want to do it? Well, then I would have to say that you have absolutely no fucking leverage because I. AM. THE HOMELANDER. And I really can do whatever the fuck I want.
Billy Butcher invokes the trope as justification for his hatred of all "supes", most prominently expressed during the group therapy scene. How much of it is genuine and how much is just an excuse he uses to deal with personal trauma is left for the viewer to decide.
The Tenth Doctor's turn as the "Time Lord Victorious" in 2009's "The Waters of Mars" has him attempt to change a fixed moment in time — one that's crucial to the history of humanity in the larger universe — to save doomed lives, justifying it on the basis of being the Last of His Kind. The problem is that changing a fixed moment threatens the universe with a Reality-Breaking Paradox, and in the end that's only prevented via a woman's suicide. The resultant changes his actions manage to make are all for the worse, and he doesn't fully redeem himself until the next story, "The End of Time"... which is also his last, not counting "The Day of the Doctor" set earlier in his timeline.
It's revealed in 2013's "The Name of the Doctor" that the central character's title of "The Doctor" is his self-imposed promise never to succumb to this type of behavior, but rather to be "Never cruel or cowardly. Never give up. Never give in." (As he puts it in the next story, "The Day of the Doctor".) In several stories, he does temporarily break that promise, and always when he has no companion serving as a Morality Pet. He always comes back to his best self, but usually at a cost.
The War Doctor, of "The Name of the Doctor" and the 50th anniversary special "The Day of the Doctor", was an extended example of this happening to him. Happily, the ending of the latter reveals that he and his other lives later managed to save Gallifrey rather than destroy it.
Over the course of 2015's Series 9, the Twelfth Doctor becomes increasingly frustrated with his nigh-immortality meaning he ultimately loses everyone he comes to care for and others besides. He becomes increasingly desperate to protect his companion Clara Oswald and to save others no matter how risky the means are, resulting in him immortalizing a human girl, Ashildr — which causes him trouble down the line. This sets up the Series 9 finale "Hell Bent", in which he becomes The UnfetteredWoobie, Destroyer of Worlds in the wake of captivity, torture, and the death of Clara. Said spoilered event is another fixed moment in time that he attempts to undo, arguing Dude, Where's My Reward? with regard to all he's done for others at one point. Perhaps because he follows the "Never give up. Never give in" part of his credo a little too well this time, in the climax he revises it to "Never be cruel and never be cowardly. And if you ever are, always make amends" as he returns to his best self with a little help from a Mind Rape that made him forget Clara ever existed.
In Heroes, the fear of this trope coming into effect is partly the motivation of the Company. They fear that if allowed to go unchecked, superpowered people will cause destruction and chaos. This fear is later revealed to have been brought about by a case of this trope; Linderman and a bunch of other people with powers decided to work together as a team to help the world, only for several members of the group to betray the others and use their powers for evil. The Company arose to prevent such an incident from happening again.
In The Falcon and the Winter Soldier, this is the reason Baron Zemo is opposed to the existence of superpowered beings, as he believes that anyone who seeks and gains superpowers has an inherently supremacist mindset. With this mindset, he executes the HYDRA scientist who recreated the super-soldier serum and smashes all the vials of serum he could find. He's soon proven right after John Walker takes the last vial of the serum and ends up killing a defenseless man in cold blood in front of hundreds of eyewitnesses. While he concedes that the super-soldier serum never corrupted Steve Rogers, he also notes that there has been no one like him since.
The whole plot of Misfits is based around a group of super-powered teenagers that are forced to contend with other super-powered people who are bound to abuse their powers. This is stated from the very first episode and becomes a point of conflict when Kelly scorns Seth for selling powers due to the chaos that would ensue.
The Earth-2 Metropolis is terrorized by Clark Luthor (Ultraman), an acknowledged vigilante and murderer.
The Superhero Registration Act story arc is caused by certain people convincing the government that superheroes will all become this trope if left unchecked.
This also happens in season 9, in the Bad Future where Clark has failed to stop Major Zod from turning the sun red and giving his troops artificial superpowers from the stolen sunlight.
In "Space Seed" and Star Trek II: The Wrath of Khan, Khan and the Augments were genetically engineered superhumans created by a cabal of scientists; their enhanced abilities resulted in enhanced ambition, leading to them betraying their creators and launching a worldwide conflict in which rival warlords fought one another while treating normal humans like slaves. Their defeat led to laws restricting the genetically enhanced in Federation society, which nearly ends the career of Dr. Bashir (whose parents had him illegally enhanced) on Star Trek: Deep Space Nine.
Star Trek: Enterprise eventually shows that the real problem with the Augments is the process was defective: The changes made to their brains that gave them greater intelligence also made them emotionally unstable and poorly equipped to deal with the consequences of physical and intellectual superiority to other people. The results were... unfortunate.
A number of other examples show up in the series, going back to Gary Mitchell in the second pilot:
Kirk: You were a psychiatrist once. You know the ugly, savage things we all keep buried, that none of us dare expose. But he'll dare. Who's to stop him?
