There are numerous synonyms for the term "deadly enemy/foe/rival", which can be used in a variety of different situations. Some common alternative terms include nemesis, adversary, antagonist, opponent, and competitor. These words all indicate a level of animosity or hostility towards someone, and may be used to express a deep-seated hatred or animosity towards an individual or group. Other synonyms for "deadly enemy/foe/rival" include archenemy, scourge, rival, and adversary. These words suggest a level of intensity or danger associated with the individual or group in question, and may be used to express a sense of urgency or importance.