It is always important to have a strong vocabulary, and one key aspect of this is knowing synonyms for commonly used words, especially when it comes to writing. When it comes to the term "fighting machine", there are plenty of alternatives available. Some possible options might include "warrior", "combatant", "soldier", "fighter", or "battleship". Other possibilities might include "champion" or "conquerer". Depending on the context, you could also consider more specific terms, such as "tank" or "jet". Whatever word you choose, make sure you consider its connotations and nuances to ensure it is the best fit for your writing.