The excuses people make for Spiders are really sad. This is basically a group of above average guys who finds strength in numbers to cover their weakness and yet people act like they're a collection of 13 Hisokas. Hisoka's original motivation to join up with Kurapika is that he noted Kuroro ALWAYS has at least two other guys by him when he makes a public appearance. Hisoka is someone who is absolutely sure of his superior tactics/trickery/strategy, but even he came to the conclusion of '1 on 3 is probably going to suck'. This implies having strength in numbers is huge as even someone like Hisoka who is crazy enough to try to fight Netero still wants to avoid 1on3 odds, so the Spiders operating with their 13 man crew does not get to cry about how Kurapika has a couple advantage when he's doing the fighting by himself.
Further, Hisoka teamed up with Kurapika with only the intention of using him, and he actually made it quite clear. He said he won't fight with Kurapika on his side. He will provide info but otherwise Kurapika is on his own because Hisoka, after all, is only interested in fighting Kuroro.
Hisoka also only knows two people's ability (Ubogin and Shizuku). That means there are at least 3 other Spiders that was supposed to have been killed by Kurapika while he has no idea what their ability is. Pakunoda and Shalunark's death sentence does not allude to Hisoka at all, so Kurapika must have done all the work there.
Kuroro's decision after he read the prophecy was to immediately pull out of Yorknew to avoid a confrontation with the Chain Assassin, yet apparently Spider fanboys view Kurapika as someone the Spiders can easily beat 1on1. Note that the prophecy doesn't even say whether Kurapika was going to die or not, suggesting there's a high probability Kurapika would get away with butchering half of the Spiders. And this is when Kurapika still isn't focused solely on killing the Spiders. It's easy to control another person. For example when Spiders talked about how Ubogin didn't return, Kuroro remarked 'it'd be very bad if Ubogin was controlled by the enemy'. I mean there's an entire school called 'Manipulation' so why would you ever assume it's hard to manipulate another person? When Werefin threatened Ikalgo to surrender, Ikalgo figured that if Werefin was a manipulation user he can easily get whatever info he want which is why he rather die than surrender. Palm was also supposed to commit suicide ASAP to avoid leaking information. Throughout HXH you see that people generally operate on the assumption that the enemy can always get whatever information they want out of a captured person because manipulation just isn't very hard to do.
Judgment Chain is a very weak 'control' type ability, and Kurapika knows this, which is why he set it so that he will know whenever Judgment Chain is removed. We can see that he clearly doesn't expect Judgment Chain to last forever, so it's not like he's thinking 'yep nobody can possibly get out of Judgment Chain'. No, he's well aware of their limitations. In fact when Killua warned him about this vulnerablity his reaction is 'why do you think I didn't know these chains can be removed?' If you look at Kurapika's reaction after getting the call, he's fully expecting Kuroro to look for an aura remover at some point.
So why did he even bother with this abilty if he knows Kuroro will eventually get out of it? Because he wants Kuroro to know what it's like to lose his friends and hopefully he might understand the pain he causes to others. Kurapika is someone who is strongly against capital punishment. He asks Ubogin why is it he can kill without feeling anything and we can see the senseless killing mentality that Ubogin has is completely beyond Kurapika's understanding. Even if the Spiders cannot be reformed, Kurapika would rather have them locked up in a cell somewhere because he doesn't believe in death as the ultimate revenge. This is what limits his ability because it is way harder to capture/subdue a person compared to just killing them outright (if you can subdue a person you can definitely kill them, but the reverse sure isn't true), and he's going to be scarily powerful if he ever decided that death is the only punishment fit for Spiders. His view on life in general is far more crippling than his alleged weakness of overvaluing friends.
