@RobbyBevard:
If they kill him, his nen ability might become even worse in death, especially since its so specifically targeted at them. They're aware of him now, so they'll try to avoid him, rather than agitate him further.
If he arrives on their doorstep again, they might do their best to capture him and restrain him in an inescapable location and feed him ocassionally, or use a nen remover on him… but they're not going to seek out a direct confrontation or try to kill him. Not as straightforwardly as that.
Maybe.
After the Nen remover removes the Chain from within Kuroro's body, they'll be able to use Neon's prediction ability again, have recruited at least another replacement, and be faced with letting someone who has it out for them specifically being allowed to run around as he pleases. They may be biding their time until a better chance to deal with him arises, and thanks to Pakunoda and Ubougin's deaths they now know everything there is about Kurapika's nen and can come up with any number of countermeasures for it: like Phinks remarked when he and Feitan ran into Gon at the auction after one where the Godfathers were killed.
But Kurapika (if he even still feels motivated to kill the Spiders rather than just collecting the eyes of his clan) would be alerted if the nen chain was removed, but at least knows the spiders would be looking for a Nen remover, and is probably trying to look into countermeasures of his own…