The phrase "twisted the knife" refers to exacerbating someone's distress, often to a point of cruelty or sadism. Synonyms for this phrase could include "rubbing salt in the wound," "piling on," "adding insult to injury," "kicking someone when they're down," or simply "hurting someone further." Each of these expressions convey a sense of cruelty or malice towards someone who is already suffering, indicating the speaker's lack of empathy or compassion. Understanding these synonyms can help us identify situations where someone may be intentionally causing harm, and allow us to intervene and provide support to those in need.