Attractive :

Loathsome : causing hatred or disgust, repulsive.
Abominable : causing moral revulsion or alteration, slimy, sordid, disgusting, sickening, odious.
Repugnant : extremely distasteful, unacceptable.
Repulsive : archaic lacking friendliness or sympathy, lacking attraction.
Attractive : pleasing or appealing to the senses, pleasant, engaging, captivating, fetching, attractive, charming.

Antonyms of Attractive is Repulsive.