Unrightful can be defined as something that is not just or legal. Its antonyms would therefore be just or legal, which refer to actions or intentions that conform to the principles of justice and legality. Some other antonyms of unrightful could include lawful, righteous, legitimate, proper, and valid. Each of these words describes something that is morally or legally acceptable or authorized. It is important to have knowledge of such antonyms to help us describe situations in which actions or decisions are justified, fair, and legally valid. By understanding the antonyms of unrightful, we can make informed decisions in our daily lives.