In the strictest sense, the conflict between man and the supernatural can be described as a conflict between man and anything that is not of nature. Supernatural is defined "that which is beyond nature or explainable by natural law." Bram Stoker's novel "Dracula" is a good example of a man versus supernatural conflict because Dracula is a character who defies nature.
It is important, however, not to confuse supernatural with paranormal. Paranormal specifically applies to those things or occurrences outside of nature that defy all scientific explanation. Paranormal is a realm within the supernatural. Superpowers are an example of things that are supernatural, but may or may not be paranormal. Spiderman's ability to spin webs in not natural, but it is ultimately scientifically explainable. Peter Parker was bitten by a radioactive spider. In this regard, it is also important to understand that "scientifically explainable" may be relevant within an established world in fiction. It is also possible for man versus the supernatural to cross over into other major plot conflicts. In this way, it sometimes functions as a sub-conflict. A plot that involves a man versus God conflict, for example, can also be classified as a man versus the supernatural conflict because God is not of nature. The two plot conflicts are not synonymous, however, because all things supernatural are not found within God.