Uncredible (adjective)
Not credible; that cannot be believed.
“a parade of uncredible witnesses”
Incredible (adjective)
Too implausible to be credible; beyond belief; unbelievable. from 15th c.
Incredible (adjective)
Amazing; astonishing; awe-inspiring.
“He was so wrapped up in watching the incredible special effects that he couldn’t keep track of the story.”
Incredible (adjective)
Marvellous; profoundly affecting; wonderful.
“I had such an incredible slice of pizza last night that I simply can’t think about anything else.”
Wiktionary