The term "most retributive" refers to something that is characterized by a severe punishment for a wrongdoing. If you're looking for synonyms for this term, there are many words that you could use. Words such as punitive, retaliatory, corrective, vengeful, avenging, or punitive could be used to describe something as retributive. Other words such as vindictive, revengeful, and retributory are also great synonyms for the term. These words often describe a punishment that is intended to make the wrongdoer feel the same pain or hurt that they caused to their victim. Overall, pick the synonym that best describes the context you are writing in, but be careful not to imply anything too violent or harmful.