The answer of course is no, because he would overshadow the main character and the reader cannot possibly root for the bad guy.
I have trouble digesting this because I find my time when writing a murder story is dealing with the reasons why the murderer kills, how he successfully gets away with it and how he deals with his family, while having a twisted mind. So I do give the murderer a viewpoint. It allows the reader to get to know him.
But I have to keep in mind that he must not become a moral character and change for the good. He must remain evil or the reader might get to like him.