There are several synonyms that can be used instead of the phrase "become furious". These include "rage", "explode", "boil over", "seethe", "fume", and "burn with anger". Each of these words can convey a sense of intense anger and frustration, and may be more appropriate depending on the context. For example, "explode" might be more fitting when describing sudden and explosive anger, while "seethe" might be better when describing anger that simmers beneath the surface for a longer period of time. In any case, these synonyms can add color and depth to your writing, helping you to convey more nuanced emotions and feelings.