Final answer:
The word that is most nearly the opposite of 'credible' is 'unbelievable'.
Step-by-step explanation:
The word that is most nearly the opposite of 'credible' is unbelievable. Credible means believable or trustworthy, while unbelievable means not believable or hard to believe.
For example, if someone tells a story that is filled with made-up events and unrealistic situations, we might say that the story is unbelievable. On the other hand, if someone tells a story that is based on true events and backed up by evidence, we would say that the story is credible.
Therefore, the correct answer is 'unbelievable'.
Learn more about Opposite words