I'm not a chemist but it seems that Novichok is the poison with the worst track record. It was claimed that this is extremely dangerous military grade neuro agent, but currently from six people claimed to be poisoned with it only one died.
I'm starting to wonder why the Russian secret services blamed using it against political opponents, try it again and again. It is completely possible that they want not to kill, but just to intimidate, but also it is completely possible that the "Novichok" is just a propaganda weapon of the West.