The phrase "more fifty-fifty" suggests an even chance of something happening or being true. Some antonyms for this phrase could include "unequal," "imbalanced," or "lopsided," which imply an uneven or unfair distribution. Other antonyms could include "certain," "definite," or "sure," which suggest a high likelihood or probability of something happening. "One-sided" or "biased" could also be antonyms for "more fifty-fifty," indicating a lack of balance or impartiality in a situation. Ultimately, the choice of antonym will depend on the context and meaning of the original phrase.