Most likely to succeed
Brazilian wandering spider (Phoneutria nigriventer)
Receiving a bite from the highly aggressive Brazilian wandering spider, also known as the banana spider, will result in ER-worthy inflammation and paralysis and, if not treated properly, death. And, oh yeah, a most noticeable symptom for males who endure a Brazilian wandering spider bite is a wildly uncomfortable erection lasting four hours or more. Yessiree, the venom of the Brazilian wandering spider, widely regarded to be the deadliest and most venomous spider on Earth, contains Tx2-6. This toxin is known to stimulate priapism (that aforementioned painful and persistent erection), a disorder that can lead to impotence and permanent damage. But thanks to modern science, the deadly venom of meandering Brazilian wandering spiders may one day serve as a marital aid — nature's Viagra? — as researchers study its potential blood-boosting usefulness in erectile dysfunction treatments.