The term "most unrightful" can be defined as something that is highly unjust or unfair. The antonyms for this word can be "just," "fair," "legitimate," "reasonable," "proper," "equitable," "honorable," "righteous," and "upright." These terms denote a state of fairness, righteousness, and justice, where things are done in accordance with the laws and principles of morality. For instance, if someone has been wronged, it is only fair and just to compensate them for their loss. Similarly, if someone has been accused of a crime, then a legitimate and reasonable investigation must be conducted to prove their innocence or guilt. These antonyms highlight the importance of righteousness and justice in society.