User blog comment:Prince of Erebor/Weakest Nen ability/@comment-4637768-20151017044751

i don't think weak is the term he is looking for... maybe he means a "bad" nen ability...

The great thing about HXH is that even a weak ability can be really strong if the conditions are met, the obvious example is Kurapika Chain Jail, his chain is a good abilitie and really versatil.

A bad ability and his deadly consecuences is by example Castro Twin... Hisoka oblitare him because he wasnt a materialization user.

the minors characters like the three guys from the heaven towers like Gidou.... Those guys were weak beacuse they were baptised... and because of that their bodies had deformations... Gidou has no legs, one cannot walk, and another lose an arm. that was because they had bad nen initiations but their abilities match their nen description and charactheristics so their abilities arent weak at all but arent great nether.

So, i think that so far, Castro is the only guy in the whole series with a "bad" nen ability.