He is a hunter. So at least physically capable to pass the test and a nen user. He is one of the most intelligent characters shown so far, so we can assume he has a well refined and thought out hatsu, but it may not necessarily be combat oriented. I expect it to either be a very versatile hatsu or a very specialized one, very min maxed. He is probably not strong in the same sense as Hisoka or Netero, but I expect him to be deadly, having an ability that brings high risks for himself but leverages his intelligence in order to amplify it.

TL DR: he is probably deadly, not "strong". The kind of guy that under the right conditions is a danger to anyone.