What is a prefix for credible?

There isn't a common prefix for "credible." However, there are some ways to create a related word using prefixes:

* Incred - This is a prefix that can be used to create the word "incredible," which means "unbelievable" or "amazing."

* Dis - While not a direct prefix for "credible," "dis" can be used to create the word "discredit," which means "to damage the reputation of."

If you're looking for a word with a specific meaning related to "credible," it might be helpful to provide more context about what you are trying to express.