1
general::
Phrase(s): a hell of a someone or something [and] a helluva someone or something
1. Inf. a very bad person or thing. (Use caution with hell.) • That’s a hell of a way to treat someone. • He’s a hell of a driver! Watch out! 2. Inf. a very good person or thing. (Use caution with hell.) • He is one hell of a guy. We really like him. • We had a helluva good time.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, one hell of a 1. See DEVIL OF A. 2. This phrase is used as an intensive to emphasize certain qualities about the noun it modifies. By itself the idiom is ambiguous, for its exact meaning depends on the context. For example, He is a hell of a driver can mean either that he is very skillful or that he is a terrible driver. Similarly, We had one hell of a time can mean either that we enjoyed ourselves greatly or that we had an awful or difficult time. [Second half of 1700s]
American Heritage Idioms