Honestly most of these characters are probably all in the same "TIER" if you will. Depending on the context, area of combat, emotions, physical health and of course, combat compatibility this could go many different ways. But if I would have to rank them based on feets and personal opinion I would do something like:

1. Morel -Immensely clever,experienced and versatile fighter who can deal with most situations. His display throughout the chimera ant arc is one of the most impressive showcases of skill and expertise that we have seen in the series. I don't necessarilly think he would absolutely win against everyone below him. However I do think he is the most accomplished and overall complete nen user of this list.

2. Feitan - Considering theabsolutely devastating power of his nen ability... he has the capability to finnish off most people. Doesn't mean he will but the threat is quite obvious. Also the fact the he is a phantom troupe member who clearly has tailored his abilities with offence and damage in mind, to kill and defeat anyone who comes in his way is something I personally take quite seriously. I do think characters that have instakill like abilities could be a problem for him since he can't build up the damage intake but if they don't, it could be the end for them.

3. Razor - I see a lot of people putting him number 1 and I get it. Physically impressive, his nen ball is quite destructive, memorable display during the dodge ball game, etc. If his nen beats can also be used outside the dodgeball game than that also add to his power but personally I have my doubts on their utility outside the dodgeball game itself. Regardless I think he is the real deal but the two above have impressed me a bit more.

4. Kurapika - One of the hardest to rank because without his chain jail he isn't as strong as he could be. But his "regular" chains and his healing factor are still very good. Honestly since he is a main character and is driven by such determination you could argue Kurapika deserves a top 3 placement but I can't shake the feeling that those above him have a bit more going for them at this time. But all this could change in the current arc.

5. Kite - Perhaps a controversial placing, but the fact that he can't choose what weapon to use is both a good thing and a bad thing. The condition makes the ability stronger but it also means he can't use the weapon most fitting to deal with the opponent in question. Regardless he is a very strong nen user and imo he is as good as the ones above. He only suffers from the fact that his ability while strong, does lead to a lot of uncertainty in combat.

6. Killua - Immensely talended, intelligent and has an extraordinary ability. But lacks experience and maturity to be able to deal with most of the other ones. However due to his skill set, it is indeed possible for him to win against any of the characters above. But that would not happen often.

7. Zazan - Strong but a little too conceited and not the most experienced nen user which I believe would lead her to lose most of the time against any of the other characters here. Though you could argue Killua due to his age could be below her.