I came across this in the first paragraph of an old post and cringed. First, «complete and utter» seems redundant. Perhaps it isn’t always; the two words have somewhat different definitions if very similar usage. It’s possible that one would want to specify both that something is not only totally whatever attribute is being ascribed, but that attribute in the most extreme manner.
I’m having trouble coming up with an example of that hypothetical, which leads me all the more to my original conclusion: this phrase is almost certainly redundant.