Meruem is a very poorly written character. He's the worst villain in HxH. Even Genthru is better. He has no rational motivations. We are not familiarised with the character at any point - we know next to nothing about him. He has one fight and dips. He has no wider impact on the story of HxH, he literally just exists as a big scary powerhouse who ultimately doesn't do anything in any way - a good villain is usually a foil of the main character in some way, it's literally psychologically proven that villains are more compelling when they directly oppose the protagonist in numerous ways which can be anything from motive, actions, behaviour etc. - Meruem has zero personality, no behaviours of any kind, no motivations of any kind. He's an empty shell of a villain.
Chrollo is a good villain but again I wouldn't put him above Doffy or Teach as things stand. Considering Chrollo a villain is a stretch in its own right too.
Hisoka's an anti-hero, not a villain.
Why do you wank over the Chimera Ants/arc so much? It's literally the worst arc in HxH and it's not even close.