There have been no shortage of villains in the Dragon Ball universe, with every single one of them posing a unique and significant threat to the Earth and, in some cases, the entire universe–though one of them stands above the rest as the greatest villain among them: Majin Buu.
Majin Buu is an incredibly old being of untold power who proved to be strong enough to kill gods and level planets on a whim. When compared to previous villains, it is clear that Majin Buu is the most powerful given how hard it was to kill him once and for all. Like Cell before him, Majin Buu had regenerative abilities, though Buu’s far exceeded Cell’s. Cell could regenerate any part of his body, or even his entire body, so long as one part of his brain remained intact. If that part of him was destroyed, he would die–and in the end, that’s exactly what happened. Cell was disintegrated by Gohan’s Kamehameha wave–an end that would be laughable to the likes of Buu. Buu survived Vegeta self-detonating, getting torn apart from the inside-out, and even remained alive after a potentially planet-destroying blast from SSJ3 Gotenks. While Buu’s resilience is impressive, and is one of the main reasons he’s the strongest DBZ villain (not counting any from Super, but even still, he’s up there), the reason he’s the greatest one of them all isn’t because of what he can survive, but rather what he accomplished.
In Dragon Ball chapter 508 by Akira Toriyama, Kid Buu is born. In a previous chapter, Goku and Vegeta travel inside Majin Buu and rip out all the people he absorbed to make himself more powerful–including a version of himself that was considered to be ‘good’. In the distant past, Buu was a being of pure destruction and evil, but after he absorbed a god known as the Lord of Lords, traces of goodness were introduced into his psyche, and that goodness manifested itself as this ‘Good Buu’. So, with Good Buu ripped from Majin Buu’s insides, the only thing that remained was the evilest version of Buu: Kid Buu–and he quickly earned that title by doing the one thing every other Dragon Ball villain tried and failed to do. Kid Buu successfully destroyed the Earth.
Kid Buu Destroyed the Earth, Thereby Succeeding Where Every Other Villain Failed
Since the classic Dragon Ball days, villains have been wanting to destroy the Earth, either in terms of eliminating all life on the planet or just by blowing up the planet itself. King Piccolo was probably the world’s first major threat as he succeeded in taking over the Earth temporarily before Piccolo was defeated by Goku, but during that time, he destroyed a number of cities and plunged humanity into chaos. When the Saiyans were introduced, their whole mission was to wipe out all indigenous life on Earth and sell the vacant world to the highest bidder before the Z-Fighters stopped them. Then, when Frieza came to Earth, he intended to destroy it after killing Goku, but was stopped by Trunks before he got the chance. After that, the Androids threatened all life on Earth as warned by Future Trunks, but that was before Cell rose to power and nearly destroyed the planet by-way of self-detonation.
It is clear that throughout Dragon Ball, the Earth has had some pretty close calls–but in this chapter, Buu actually does what the others were trying to do, and he blows up the entire planet. Not only that, but before he destroyed the world itself, he wiped out all life on Planet Earth (most of it with a single blast), so it was technically dead long before he pulled the trigger on detonating the whole thing. Since Majin Buu succeeded where literally every other bad guy failed, he takes the top spot as Dragon Ball’s greatest villain.