This question is actually not possible to answer with certainty, because it supposes that there is a way to measure “venomousness” in a fashion we can all agree on. Many experts answer that it is the Inland Taipan of Australia, because its drop-by-drop concentration of venom has great potency when measured by its ability to kill rodents. But this does not necessarily mean it would have the greatest ability to kill people! Nobody (thank goodness) has ever done a study to compare the relative potency of all of the venoms of the world in humans, but we know with certainty that rodents and humans have different ecological relationships with snakes. Our resistance to venoms may very well be different, too. Furthermore, venom is only dangerous if it is injected into a person effectively; so the dangerousness of a snake depends on its size, style of attack, fang anatomy, and closeness to the person. The saw-scaled viper of the Middle East kills a lot more people each year than the inland Taipan ever did.