The question is an interesting one.
If it is about feelings for a thing or person, a formal option could be "ambivalent", if it is supposed to evoke both good and bad reactions / love and hate emotions about a thing or a person.
Another interesting case could be a word, that can be interpreted to be either good or bad, and the person who used the term meant only one of those, not both. Such a word is "fantastic" and also a reason @Raku should not have used it in his answer. If I say, "John gave us fantastic support at the time of crisis", I may have meant it in a good way, that his support was really something beyond what could be expected, or in a bad way, I may have meant that his support was not of any worth, it was unreal, imaginary, fantastic.
There are similar other words, which you can think of.