World's Worst Venom

It's one of nature's most efficient ways to kill. Once injected into the bloodstream it can impair nerves and seriously damage flesh in minutes. Venom - it's a cocktail of virulent biological toxins causing searing pain in seconds. It is the weapon of choice for thousands of species, but which one is most deadly to man? Of the creatures armed with this lethal cocktail, which is more likely to kill you?