Board Thread:Questions and Answers/@comment-26005711-20151226104253/@comment-26005711-20170125153304

Seahunterr wrote: I don't think it is possible to establish clear power levels in Hunter X Hunter. There are too many parameters to deal with, this is not dragon ball.

This would be smarter to ask who would win in a fight between both. Actually, Illumi's known abilities require other humans and in battle we only use known abilities, so Hisoka would obviously win in 1v1 if we only consider known abilities. But I assume that Illumi has more abilities to show (we try to guess who'd have an advantage, even though that doesn't mean that he'll certainly win, and that includes Nen control, physical strength, experience, intelligence...). Since he's killer, he should have abilities for 1v1 combat (except needles), but we don't know them.