The antonyms for the phrase "rendered unintelligible" would be "clear," "understandable," "comprehensible," and "legible." These words signify that a piece of communication or document can be easily understood or read without any confusion or ambiguity. By contrast, if something is "rendered unintelligible," it means that it has been made confusing, unclear, or difficult to understand. This could be due to various reasons such as poor handwriting, jargon, or language barriers. In any case, the antonyms for "rendered unintelligible" emphasize the importance of clear and effective communication.