The Sydney Funnel web spider is the most poisonous spider on earth, causes comas, seizures and death within the hour of the bite. Those who believe the wandering spider is the most venomous are incorrect and it is only reported the most dangerous because there are more reported bites. Not as venomous though.
There is an urban myth that the Daddy Long Legs is the most venomous spider, but that its fangs are too small to pierce human skin. This has been proven to be a fallacy, as its venom is not actually very strong at all.
The world's most venomous spiders are the Brown Recluses and Funnel Web spiders. However, the Australian Redback spider is more venomous than the Australian funnel web spider (sometimes called the Sydney funnel web spider). The Brazilian Wandering Spider is also up with the most venomous spiders in the world.