that's a hard word to translate... as in english 'creep' typically means some sort of psycho-ish person.
'repulsivo' and 'asqueroso' don't really sound like things you would call someone, because they're more of adjectives for things... For instance, if we were talking about the smell or something, then 'repulsivo' or 'asqueroso' would sound right. For a person, i usually say 'enfermo' (works wonders) or 'sicopata' (though this might have different implications)