A detraction is the opposite of an attraction––it is something bad about someone or something. If you love peace and quiet and you’re thinking about buying a house, a location on a major road would be a detraction.
Detraction comes from detract, which means to diminish, or to speak badly of someone or something. If you run for office, it is bad form to spew detractions of your opponent’s character. Unfortunately, this is exactly how many political campaigns work. Detractions can also be interferences. The noise of the party next door might be a detraction from your attention while you’re studying.