Giving an antonym for the word attributes can be tricky, mainly because of its meaning, as in, giving credit to or being an aspect of something. Giving an opposite of, "attributed the painting to...
The opposite (antonym) of antonym is synonym. An antonym is a word that means the opposite. A synonym is a word that means the same thing, or nearly the same thing, for a given context.
Some words do not have direct opposites [antonyms]. Antonyms do not usually substitute for phrases. The phrase "you are" has no antonym. A contrasting version of "you are" is "you are not".