"Rubbing salt the wound" is a commonly used idiom that means to aggravate an already difficult situation or make someone's misery even worse. However, there are several other idiomatic expressions that convey a similar meaning. One such synonym is "adding insult to injury," which refers to making a bad situation even worse. Another popular phrase is "twisting the knife," which means to cause further emotional pain. Additionally, "piling on" or "kicking someone when they're down" both suggest that someone is being unfairly targeted or made to feel worse when they are already struggling. These phrases, like "rubbing salt in the wound," all convey the idea of exacerbating an already difficult situation.