Put simply, to dislike can be used as a transitive verb that means to "not like." Maybe you dislike spinach. But it can also be a noun, as in "You seem to have developed quite a dislike for spinach."
English being a language of trial-and-error, the word dislike came about in the mid-16th Century, as modern English was still in its infancy. At that time, some words were tried and discarded, to be replaced with others that stuck. That was the case with dislike, which developed after the word "mislike" was dropped as the opposite of "like." Speaking of prefixes, don't confuse the word dislike with "unlike," which means that something is different from something else.