Gon is the protagonist of Hunter x Hunter and easily one of the most talented characters in the series. While young, he holds tremendous potential within himself.
Viewers saw a glimpse of what Gon would be like as an adult during the Chimera arc, which indicated that he would turn into a phenomenal fighter who few can hold their own against. While there are many Hunters and other characters that would fall against adult Gon, there are some that can still rival him.
Updated on Nov. 18th, 2021 by Claris Lam: Gon is one of the strongest characters in Hunter X Hunter, doubly so in his adult form. Few characters in the series can stand up to adult Gon's tremendous power, but that doesn't mean he's invincible. There are plenty of HxH mainstays who could rival adult Gon and put him in his place.
15 Can't: Kite
Kite is a fairly experienced and powerful Hunter in his own right, considering he sacrificed himself to give Killua and Gon a chance to escape Neferpitou during the Chimera Arc. However, their ability to use the Crazy Slots could be a huge hindrance if they ever fought adult Gon. With Kite being reborn as a Chimera Ant, they need to relearn their combat abilities first before they can fight anyone, let alone an adult Gon.
14 Can Rival: Illumi Zoldyck
Illumi is an incredibly smart, manipulative, and fast assassin, which is expected of someone from the infamous Zoldyck family. His ability to use needles to disguise himself temporarily and incapacitate enemies could help him get the edge above Gon if they fought each other. Considering how long he manipulated his own brother, he could easily rival an adult Gon.
13 Can't: Machi
Machi is one of the weakest Phantom Troupe members. Even though she and the rest of the Troupe posed a threat to Gon and the others in the Yorknew City arc, Machi mainly acted as a healer rather than a combatant.
She can read the movements of her enemies, which would help her avoid a few of Gon's attacks for sure. However, her strength is poor in close quarters and would lead to her downfall when fighting an adult Gon.
12 Can Rival: Chrollo
Chrollo Lucifer is the head of the Phantom Troupe and its most powerful member before Kurapika got to him during the Yorknew City arc. Assuming that Chrollo somehow regained his ability to use his Specialist Nen abilities to steal the abilities of others, adult Gon might be in for some trouble when fighting him. Considering that Kurapika took away Chrollo's ability to use Nen without risking his life, Chrollo could still be at risk of losing to Gon if he does not figure out a way past the Judgement Chain first.
11 Can't: Ponzu
Even if Ponzu survived the events of the Chimera Ant arc, it would be impossible for her to rival adult Gon later on. Gon easily beat Ponzu during the Hunter Exam and took her badge. Gon has also grown stronger since and survived the events of the Chimera Ant arc, while Ponzu struggled to survive. This vast difference in strength and experience showed that Ponzu would likely lose to adult Gon if they met in battle.
10 Can Rival: Hisoka
Hisoka is a former member of the Phantom Troupe and has played a major role in the series to date. He's an incredibly powerful individual thanks to his Nen ability, Bungee Gum.
Hisoka looks forward to the day Gon matures as a fighter and fights him. Although he appears to be weaker than adult Gon, he isn't the finished product himself either. By the time the two fight, Hisoka will have gotten much stronger and will be able to rival Gon.
9 Can't: Leorio
One of Gon's closest friends, Leorio is one of the Zodiacs who also aims to become a doctor. Although not highly proficient in Nen usage, he's still decent at it. Even if he trains for all his life, Leorio matching Adult Gon is nigh impossible. The power difference between the two is massive as it is and with time, Gon will only get stronger at a faster rate.
8 Can Rival: Killua Zoldyck
Killua is from a famed group of assassins known as the Zoldyck family and also Gon's best friend. He's an incredibly powerful character who specializes in Transmutation type Nen ability. Killua is arguably stronger than Gon right now and holds an equal amount of potential to him. As an adult, it is a certainty that Killua will be able to rival Gon in terms of strength.
7 Can't: Meleoron
Meleoron was once a Chimera Ant Squadron Leader. Although his rank indicates he's someone with high strength, Meleoron was actually weak and considered himself on the same level as a Chimera Ant foot soldier.
That said, His Nen ability is extremely useful and allows him to make himself invisible as long as he holds his breath. He can also extend the invisibility to others, however, only for a set amount of time. It is quite obvious that Meleoron stands no chance against adult Gon.
6 Can Rival: Kurapika
Another one of Gon's friends, Kurapika is one of the Zodiacs just like Leorio. He's an incredibly strong Nen user who excels in Conjuration based techniques. When using Emperor Time, Kurapika gains compatibility with all the Nen types, meaning he can fully master everything. He's proven powerful enough to fight and defeat the likes of Uvogin of the Phantom Troupe. As an adult, it is highly likely that Kurapika will be comparable to Gon and Killua since he has a lot of room to grow.
5 Can't: Nobunaga
A member of the Phantom Troupe, Nobunaga is a decent swordsman and an admirable Nen user. He seems be well versed in En and his other skills make him quite useful in a fight.
While strong, Nobunaga is nowhere near the level of a Chimera Ant Squadron leader like Leol. Meanwhile, Gon was comparable to Meruem, the King of the Ants himself. It is quite clear that Nobunaga would be no match for adult Gon.
4 Can Rival: Ging Freecss
Ging is Gon's father and a double star Hunter, which means he's way more experienced than his son. Although little has been seen of his abilities, he's one of the top 5 Nen users in the entire series based on what Isaac Netero thought of him.
Ging's powers haven't been revealed yet but we believe that he'll be more than capable of matching Gon in a fight. It is possible that Ging could be as strong as Netero, which means Gon would have a worthy competitor in his father.
3 Can't: Knuckle
Knuckle is one of Morel's students and played a major role in the Chimera Ant arc of the Hunter x Hunter series. Knuckle is extremely powerful, as seen when he managed to defeat Gon in a fight.
While he's stronger than Gon now, Knuckle would not be able to defeat him as an adult. In his fight against Menthuthuyoupi, Knuckle struggled while Gon manhandled Neferpitou without any trouble whatsoever.
2 Can Rival: Isaac Netero
Isaac Netero was the former chairman of the Hunter Association and the strongest known Hunter in the series to date. In his prime, he was at least twice as strong as he was in his old age when he fought Meruem. Netero was able to rival Meruem in battle, which is something even the King acknowledged. Had he been alive, he would've been able to rival Gon in a fight as well and he'd certainly put up a good fight.
1 Can't: Kalluto
Just like Killua, Kalluto is a member of the Zoldyck family. He currently serves as a member of the Zoldyck family and is exceptionally powerful, but he's not that strong compared to Killua. It wouldn't be a stretch to say that Kalluto is also weaker than Gon is right now. His chances of rivaling adult Gon are extremely low. If the two were to ever fight, the battle would end in Gon's favor within minutes. Nonetheless, Kalluto isn't one to be underestimated.