Who wins between Killua and Kurapika

Is there a user who could have defeated Meruem (the King)?

Throughout the hunter series there are people who are speculated to be in the power of the god class. Meruem himself is of course such a being. Alluka is another obvious example. I can list a few others in this category to give you an overview. In my opinion, the only way to defeat the Ant King is with the power of such a class.

Don Freecs (Ging's grandfather) is a character to whom such a level of power can be ascribed. He is strong enough to live permanently on the dark continent. Constantly mapping and mapping the area and writing books about the species and wonders found there. Mind you, the chimera ants come from the dark continent. The continent contains creatures so deadly that they make the chimera ants seem like insignificant miniature ants in comparison. In order for a user to be powerful enough to reside there, they must be a good contender to fight and defeat Meruem.

Kite's new identity as Meruem's sister gives her the immense abilities of a chimera ant princess, effectively placing him in the category of god classes capable of fighting an ant king.

While not confirmed, there is reason to believe that the Sonata of Darkness that deformed Melody was not written by the devil himself, but in fact by a nice user whose power is so hideous that it can easily be called diabolical could. A being of such power could also make a good contender against Meruem.

If someone of Netero's power level (for example someone from the legendary Seirin group) applies a Nen restriction (i.e., takes a leaf from Gon's book) during combat, that person should be powerful enough to defeat the Ant King.

In his heyday, Maha Zoldyck was an assassin as we have never seen him before. There was almost no method of death in the Grim Reaper's arsenal that Maha could not dish out. He would be the only one I would tip in order to be able to live successfully on the dark continent (apart from Don Freecs, of course). in fact, "god class" was not outside of his jurisdiction. Given that Netero "survived" a fight with Maha, the Ant King would most likely survive it too. They might be the same in battle, but I doubt Maha could dish out a real loss.

There are skills in the hunter universe that could instantly turn you into a god-level fighter. In fact, I believe Killua even mentioned one in the Greed Island arc when he stated that the combination of risky dice and capricious spirit could make an individual quite powerful. It would be similar or the same effect as someone wishing Alluka gave them a power / ability / strength that can defeat the Ant King.