Summary
Dragon Ballhas continuously introduced new villains into the main story who always end up being stronger than the villains of the arcs before it. This system is what has led to the series having so many different and powerful transformations for the main characters, as these constant power-ups are needed for the heroes to get stronger in order to measure up to each new villain that is introduced, as they’re always the strongest up until that point.
This trend, however, changed for Beerus inDragon Ball Z: Battle of Gods. This is because, ever since his introduction into the franchise, the heroes have never faced someone as powerful as him, even in the subsequent arcs ofSuper. His nature as a God of Destruction has put him on a level far beyond anything that the heroes can compete with,even in their most powerful forms, so could it be that Beerus ends up as the series' final villain?

Story Arc
God of Destruction Beerus Saga
Beerus' introduction into the series took many fans by surprise, as it not only showed an incredibly powerful new character but also because it opened up a whole new avenue of power in the franchise that no one even knew existed. By introducing a deity with such incredible power, fans were quite taken aback when they found out that someone far stronger than even Super Vegito and Majin Buu existed in theDragon Balluniverse.
This surprise was later compounded when Beerus was shown to blow up half of an entire planet with a simple tap of his finger. This action was enough to initially cement him as an evil villain who had awoken from his slumber to fight and defeatthe legendary Super Saiyan God, which brought him to Earth and face-to-face with the Z-Fighters. Although Goku unlocked this form and fought well enough against the Destroyer in a close fight, it was revealed that Beerus wasn’t even trying during the clash and ended up defeating the Saiyan.

Although he didn’t destroy the planet and ended up becoming somewhat of an ally to the Z-Fighters, Beerus' fickle nature leads to him being quick to anger. It doesn’t take much for Beerus to get him riled up, as even a slight disagreement over food can cause him to completely change his mood, becoming a destructive and violent monster, as was seen in his fight with Buu in the movie.
Moreover, Beerus is a Destroyer God above all else. Though he is lazy and dismissive of his responsibilities, hisjob requires him to destroy entire planetsand civilizations that are hindering the progress of the universe in some way. If Earth, or any other planet allied with the Z-Fighters, comes to be the next one that Beerus has to destroy, it would be at direct odds with Goku and friends. After all, the Granolah Arc revealed that it was indeed Beerus who ordered the destruction of Planet Vegeta and all the Saiyans.

What Could It Mean For The Heroes?
Though Beerus is an extremely volatile character whose nature is to destroy planets and civilizations, he is an ally of the main characters. More than that, Goku and, more directly,Vegeta both consider him to be a mentor figurethat is integral to their evolution as fighters, standing as a goalpost for them to reach in strength.
As of Chapter 102 of theDragon BallSupermanga, Beerus has already confirmed that the Saiyans still aren’t as powerful as him, so they couldn’t really do much to stop him if he does oppose them. Though his turn is unlikely as of now, Beerus' anger and nature as a Destroyer make him a character whose entire being is supposed to be unpredictable, offering a massive challenge should he ever go against the heroes.
And once you’re stronger than me? I’ll nominate you as the next God of Destruction.
Goku has unlocked the technique of the Angel’s, called Ultra Instinct and, under the tutelage of Beerus himself, Vegeta can utilizethe power of the Gods of Destructionin his Ultra Ego form. Wielding these divine techniques, the Saiyans are stronger now than they have ever been, so a coordinated effort against Beerus would be their best bet. However, they still wouldn’t be able to do much as Beerus’s true strength is still a mystery, as he is thought of as the most powerful God of Destruction.
The only way that any sort of danger could be presented to Beerus by the Saiyans is through a fusion in their strongest forms. With Gogeta or Vegito holding the power of the Angels and Gods at the same time, they may hope to match Beerus, who is hinted as the only one of the 12 Destroyers who can use even a semblance of Ultra Instinct. Even then, however, Beerus may break out a new power that is far greater than anything fans have ever seen before.
How Likely is This to Happen?
In truth, there is a very slim chance of Beerus turning away from the side of the heroes. Despite his nature and his job, he has expressed a fondness for Earth and his new disciples, making it so he probably wouldn’t hurt things of his own interest anyway. Besides,even if they ever surpass him, he is more than willing to nominate them as the next Gods of Destruction for Universe 7, showing that he has no qualms against them.
More than turning into a villain for them to face at the end of everything, Beerus would likely face them as a final test of their strength. His primary motivation inDragon Ball Z: Battle of Godswas to fight someone without holding back for the first time in millions of years, and although this wish didn’t exactly come true, he saw potential in the Saiyans to make this dream a reality for himself, so if they are ever to fight, it would likely be at the end of Beerus’s career as a Destroyer God.