Most experts consider the Funnel Web Spiders to be the deadliest spider in the world. Bites from the Funnel Web spider have also has been known to kill humans, but since the discovery of Funnel-web antivenin in 1980, very few people if any have died from being bitten by a Funnel Web spider.
The Brazilian
Wandering Spider is could probably be considered to be the world’s 2nd deadliest spider. A
bite from a Brazilian Wandering spider (or any spider for that matter)
won't likely kill a human instantly, and only a small number of deaths
have been recorded due to being bitten by a Brazilian spider (less than
1% of bites kill humans).
Most people think of a Black Widow spidere to be the deadliest in the world, but is not considered to be the deadliest. However, in the United States the two deadliest spiders would be the Brown Recluse spider and the Black Window spider.