Hunter x Hunter features a variety of strong characters who display formidable fighting capabilities and Nen. However, none introduced in the anime or manga so far are as intimidating as the Ant King, Meruem. As the main antagonist in the Chimera Ant Arc, Meruem was a figure who existed for approximately only 40 days.
However, within this time, he grew at a pace frightening enough to threaten the entire world. As a result, it is no overestimation to call Meruem the most powerful character in Hunter x Hunter. He is not merely a physical powerhouse but also a highly intellectual figure whose strength transcends the traditional definition of power.
Meruem, the masterpiece of the Ant Queen, commanded the fear and respect of all other ants right after his birth. Even the powerful royal guards recognized his authority and served him faithfully. Soon after, he showcased his ruthlessness by killing and eating men, women and children alike.

In the first part of his life, Meruem was majorly known for his mercilessness and physicality, where he could overpower others with just brute strength.
However, with time, he accumulated knowledge and strategic prowess. He could easily learn complex games such as Gungi and delved deep into thoughts about humanity and morality despite being classified as a “monster”.
Due to this, he didn’t grow only in strength, but also in maturity. As a result, even many of the Hunters struggled to see Meruem as evil and only fought him since it was their duty.
Meruem’s senses, strength, and speed are not measurable because he has never been pushed to his limits. He could effortlessly fight Netero and was not damaged by his opponent’s 100-Type Guanyin Bodhisattva. Meruem is extremely fast, has never shown to be in pain, and is never tired. Combining these with his prowess in physical combat, no one stands a chance in a direct battle against the Ant King.
Additionally, Meruem is extremely talented in Nen and his special ability is among the most broken in Hunter x Hunter. His aura is potent enough to overpower even Netero and his level of mastery in controlling it is unparalleled. Meruem is mainly an Emitter, but he can use various other types of Nen.

His primary skill is called Aura Synthesis, where can grow by consuming others. Mainly, when Meruem eats a Nen user, his own aura expands. This makes his potential limitless. Along with this, when he consumes enough of a target's body, he can also use their distinctive Nen abilities. This was seen when he consumed Youpi and Pouf to metamorphose.
Through this, Meruem gained wings to fly at great speeds and could even perform the powerful Rage Blast. Due to his intellect, he drew inspiration from his subordinates’ skills and came up with his own version of Spiritual Message. This involved spreading his aura in the form of small photons. As these particles scattered, Meruem could gather information about everything they came into contact with.
As mentioned earlier, along with his skills, Meruem is extremely smart. This is to the degree where his intellect possibly overshadows his strength. Consequently, he could quickly learn new skills, defeat national champions of games like chess and shogi, and adapt to Netero’s moves during their battle.
Are there any characters stronger than Meruem in Hunter x Hunter?
At this point, it is hard to say that any character in Hunter x Hunter is as strong as Meruem. Within just a few days of existence, Meruem had managed to become the greatest threat in the series. Even the Chairman of the Hunter Association, Netero, realized he couldn't defeat him.
Hence, the only way to beat the Ant King was by poisoning him through the Poor Man’s Rose. Even then, Meruem survived for a long time due to his enhanced physicality. His potential to become stronger was limitless, which is exactly what made him so fearsome.

However, there are also contenders for his place as the strongest, based on how one defines “power.” For instance, Nanika from the Dark Continent can grant wishes no matter how impossible they might seem. While Meruem died of poison, Nanika could have easily healed it if she had been present. At the same time, there needs to be an external party that grants Alluka’s requests for Nanika to appear.
The Dark Continent creature also cannot use the wishes for herself, making it useless in direct combat. Similarly, the extent of Gon’s rise in power when he uses Limitation Transformation was never measured. Pitou notably mentioned that his powers had reached that of Meruem.
Though this isn’t a very fair comparison since Gon used a Vow, it gives room for a debate should Gon regain his Nen and permanently reach his “Adult form.”
Meruem is the strongest character introduced in Hunter x Hunter so far and displayed terrifying potential despite living for only a few weeks. His growth was limitless and he was never beaten in a fair battle. Due to this, Netero was forced to kill him deceptively.