This question is quite controversial. We can just list the strongest characters because strength id determined by many different factors. For me, the best character so far is Meruem, the king of Chimera Ants. He’s stronger that Netero although the latter is said to be the strongest of the Zodiacs he died in a fight with Meruem. Beyond Netero, Netero’s son is also very powerful and has returned from the Dark Continent. I’d also mention Hisoka who’s a magician. He resuscitated himself after being defeated which shows his unique abilities.