How can real life people kill a devil?

First, it should be noted that devils and demons are not real; they are mythical creatures who represent all that is evil. They are often found in literature and in movies. Of course, some religions do believe in devils, but again, this is a belief rather than a fact. That said, in a number of works of fiction, the "good guy" finds a way to kill a devil or a demon, or to trick him and banish him back to hell. Some Christian stories assert that a devil can be killed by showing the crucifix and demanding that the evil one be gone, in the name of Jesus. It is also worth noting that sometimes, in real life, evil people are referred to as "the devil" or even as "satan"-- this is a metaphor, however, since there is no proof that even the most diabolical person (Hitler, for example) was an actual demon. And since devils are fictional, a real life person could not kill one.