The strongest Chimera Ant, the Ant King Meruem, is so far the most powerful being seen in the story, minus perhaps Ai. Even one of the best nen users in HxH, Isaac Netero, was not enough to take ...
and his character has grown from being an emotionless Chimera Ant King to becoming a compassionate friend of a human. The character growth from Meruem solidified Hunter x Hunter as a masterpiece.
Meruem, the King of the Chimera Ants in the Hunter x Hunter series, is presented as the ultimate power. He is a tremendously powerful and intelligent creature that keeps becoming stronger.