Unfriendly, a.
1. Not friendly; not kind or benevolent; hostile; as, an unfriendly neighbor.
2. Not favorable; not adapted to promote or support any object; as, weather unfriendly to health. -- Un*friend"li*ness, n.
Shades of meaning
Fernald lists unfriendly only as an antonym, under friendly, propitious.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given