Two weeks ago I talked about the importance of a good villain. NOTE: even though I framed it in terms of traditional villainy, what I said also applies to other kinds of villains, like disease, economic trouble, natural disasters, etc. Whatever your hero has to deal with needs to be powerful enough that to overcome it requires true heroism.
So, first things first: what is a hero? Lots of different definitions for that one. Webster's dictionary lists three: