It seems unfairly menacing that a snake that can literally "stand up" and look a full-grown person in the eye would also be among the most venomous on the planet, but that describes the famous king cobra! Their venom is not the most potent among venomous snakes, but the amount of neurotoxin they can deliver in a single bite—up to two-tenths of a fluid ounce—is enough to kill 20 people, or even an elephant. Fortunately, king cobras are shy and will avoid humans whenever possible, but they are fiercely aggressive when cornered.