Since the beginning of Post Timeskip, it was clearly implied that the Supernovas were really strong, the strongest among the rising pirates, that increased their strength and never stopped improving, until they actually became a recognised faction in the World Balance. Yes, the Worst Generation/Supernovas are portrayed and stated to be a faction just like Yonkos, Marines, Shichibukai and Revolutionaries.
That was a concrete reality at that point already. With the further events, we clearly see that Oda drew a massive difference even among the Supernovas.
Nowadays, strong characters are the characters with strong Haki. To have a strong Haki you need to have a strong drive, and to have that push to make you overcome your limits and push forward. There are characters with lesser will and objectives, and characters with greater will and drive to reach goals that seem impossible. This is what sealed the difference between weaker and stronger Supernovas.
The weaker Supernovas are Bonney, Capone, Urouge, Hawkins, Apoo, Drake. These are the ones who willingly accepted to submit themselves to the Yonkos, or that tried to fight them on their own but were just too weak not even for the Yonkos but for the latters’ underlings already, and after being defeated didn’t try anymore. And even when they tried to oppose the Yonkos, they didn’t have neither the guts nor the actual power to do that personally and with an open challenge. Also, no one of these characters has a special drive to reach the top in the One Piece world. Being just “strong” for them is ok.
The strongest Supernovas are Killer, Kid, Law, Zoro, Luffy. These are the ones who never even thought to submit to the Yonkos. These are the one who were strong enough to defeat or at least fend off the Yonkos’ underlings. These are the ones who dared to openly challenge and fight the Yonkos, and that even when they were defeated, instead or giving up, decided to improve and to come back for the rematch. All of these characters have a drive to excel and to reach the absolute top levels in the One Piece world.
Also, all of these characters have traits in common: Law is a D and has one of the strongest devil fruits in the world, Luffy and Zoro on a side and Kid and Killer to another make two couple of Captain and First Mate/Right Hand/Vice Captain that have a very close relationship in a way that remembers the Roger-Rayleigh and the Shanks-Ben ones. Luffy, Zoro and Kid also all have Haoshoku Haki, they are all Conquerors. Luffy will clearly become the Pirate King, overcoming all Yonkos and Admirals, and Zoro will be the closest ally to him, and will also become the World’s Strongest Swordsman, defeating someone who is a peer to the Yonko.
Also, Luffy has legendary benchmarks like Roger and Joy Boy, and Zoro has legendary benchmarks as well, like Rayleigh and Ryuma.
Call it a coincidence, but even in this shot from more than ten years ago, as you can see, Luffy, Zoro, Law, Kid and Killer are the ones in the center, put in a far greater relevance than the other Supernovas, who are in a less relevant position on the sides. Foreshadowing?
Luffy, Zoro, Law, Kid and Killer are the one who fought and showed exceptional feats against two Yonko.
They are the Rooftop Five. They gave us the greatness known as Rooftop Piece.
Yes, Rooftop Level is a reality. Anyone of the Rooftop Five is at the very least massively stronger than your average Yonko Commander.
Let’s see all the praise and hype that these five rising received from Kaido and Big Mom, two of the strongest characters in the whole series.
To have a reference, let’s not forget that Kaido basically bashed and trashtalked someone like Doflamingo as a weak one. Kaido also regarded the Red Scabbards as too weak to even pose a small challenge to him. Instead, this is how the Rooftop Five were regarded:
The author calls the battle between Yonkos and Supernovas as a battle between monsters.
“Powerful pirates leading the next generation…”
“Such a shame! If you joined me, we would have took the world together!”
“You were strong enough to scar me for life.”
“Your generation is trouble”
“He actually cut Kaido!” “It hurts!!”
“We’ve underestimated them!”
“Look out! Kaido!”
“It would be a shame to kill you! Whoever wins gets close to become the Pirate King!”
“You are monsters!”
“This battle is so fierce!”
“They’re more vexing than I imagined!”
“This is fun!”
“Those power of yours really throw me off!”