Luffy's generation of Supernovas are some of the most dangerous pirates to have ever existed in the world of One Piece. They arrived at Sabaody Archipelago with a bounty of greater than 100 million berries prior to the Marineford war as rookies and have, since then, gone on to become accomplished pirates in the New World.
Almost every Supernova in One Piece has made their way to Wano Country in the New World, for one reason or the other, and have thus shown their full strength to the fans in the war involving two Yonko as well.
8 Scratchmen Apoo
Apoo is the captain of the On-Air Pirates who currently has a bounty of 350 million berries on his head. At some point, he joined forces with Kaido and set up for Kid and Hawkins' alliance to be ambushed. On Onigashima, Apoo fought quite a lot of people, including Zoro, X Drake, and even the CP0 members.
Apoo's sound-based Devil Fruit allows him to hurt anyone who listens to his music. Apoo is quite powerful, however, out of all the Supernova that fans have seen on Onigashima, he's likely the least impressive.
7 Basil Hawkins
Basil Hawkins, also known as the Magician, is a pirate from the North Blue, and he landed on Sabaody Archipelago with a bounty of 190 million berries. His current bounty is 320 million berries, which is impressive.
Hawkins has the Wara Wara no Mi that grants him the ability to control straw at will. What's more, he can use voodoo magic and cause all sorts of problems for others. Hawkins also makes use of tarot cards while fighting. On Onigashima, he fought Killer and was defeated by him.
6 X Drake
X Drake is the Captain of the Drake Pirates and quite a dangerous person in the One Piece world. Although he's one of the Supernova members, Drake is actually a Marine who belongs to the secret unit called SWORD. He is quite strong and has the power of the Ryu Ryu no Mi, Model: Allosaurus.
With his Devil Fruit, he can transform himself into an Allosaurus and its human hybrid at will. Drake was a part of the Tobiroppo until recently, meaning even Kaido considered him to be quite powerful. He fought the likes of Zoro, Apoo, and even CP0 on Onigashima momentarily.
5 Killer
Also known as the Massacre Soldier, Killer is the right-hand man of Eustass Kid and an incredibly skilled pirate. He has a bounty of 250 million berries on his head currently, which makes him quite a dangerous figure.
Killer was one of the fighters who took on Kaido and Big Mom on the rooftop. Although he didn't steal the show, he did well against them and eventually fought Basil Hawkins. Despite being on the back foot, Killer was able to defeat Hawkins eventually and open up a path for Kid to fight Big Mom.
4 Roronoa Zoro
The Number 2 of the Straw Hat Pirates, Roronoa Zoro showed all of his might to the fans on Onigashima, proving that he has come really close to Dracule Mihawk's title. On the rooftop, Zoro fought Kaido and Big Mom with the rest of the Worst Generation pirates and managed to scar Kaido, which is amazing.
Later, Zoro awakened the power of Conqueror's Haki and managed to coat his swords in it, making him even stronger. Zoro then fought King and although he struggled quite a lot, he eventually managed to overcome him, though he passed out as well.
3 Eustass Kid
When One Piece's Supernova gathered on Sabaody Archipelago, Eustass Kid had the highest bounty of all at 315 million berries. Kid went to the New World immediately after the war and has done fairly well over time. On Onigashima, Kid showed the fans what he was truly capable of as he took on Kaido and Big Mom on the rooftop, managing to hurt both of them in an impressive manner.
Kid then went on to team up with Trafalgar Law and took on Big Mom in a fight that eventually saw the Yonko get defeated for the very first time in ages. His usage of the Jiki Jiki no Mi and its awakened powers was truly magnificent.
2 Trafalgar Law
"The Surgeon of Death," Trafalgar Law hails from the North Blue and is one of the most powerful characters in One Piece right now. During the Punk Hazard arc, Law agreed to team up with Luffy to take down Kaido, and on Onigashima, he managed to show his immense skill to fans. Law fought Kaido and Big Mom on the rooftop and was impressive against both of them.
What's more, Law then took on Big Mom with Eustass Kid and managed to defeat her, playing a massive part in her loss. Using the Ope Ope no Mi and its awakened powers, he inflicted fear into the Yonko and managed to break her bones over and over again. Truly, he was the key to defeating Big Mom.
1 Monkey D. Luffy
Without a doubt, Luffy is the strongest Supernova on Onigashima currently. After stepping into Wano having learned the ability to use Future Sight Observation Haki, Luffy managed to learn advanced Ryuo as well. In the fight against Kaido and Big Mom on the rooftop, Luffy was incredible and dealt a lot of damage to the former.
Luffy then went on to learn the advanced application of Conqueror's Haki and with it, was able to fight Kaido in a one-on-one for quite a while. Luffy split the heavens with Kaido, a feat that's been exclusively achieved by Yonko level characters. He's far from his full power and is still able to match Kaido in a one-on-one quite easily.