The term "fifty-fifties" generally refers to a situation where two options are equally likely, with a 50% chance of either occurring. Antonyms for this phrase could include words such as certain, definite, or uneven. Certain would indicate that one option is more likely than the other, with little to no chance of the opposite occurring. Definite implies a single outcome with no ambiguity or uncertainty. Uneven suggests that the likelihood of the two options are not equal, with one being more probable than the other. Overall, the antonyms for "fifty-fifties" describe a situation where the likelihood of one outcome is favored over another with varying degrees of certainty.