The phrase "bad egg" implies a person who is untrustworthy or has a negative influence on others. Some antonyms for "bad egg" may include "good apple," suggesting a person who is reliable and has a positive impact on others. Another antonym may be "model citizen," indicating a person who upholds high moral standards and contributes positively to society. "Gem" or "jewel" may also be used as antonyms, portraying a person who is valuable and highly regarded. In contrast, synonyms for "bad egg" may include "rotten egg," "black sheep," and "troublemaker.