If you're looking for synonyms for the phrase "unduly favorable," there are plenty of options to choose from. Some possible choices might include phrases like "excessively biased," "overly partial," or "undeservedly positive." You could also describe something as being "unduly sympathetic," "unjustly favorable," or "unreasonably favorable." Other options might include phrases like "undeservedly glowing," "unjustly one-sided," or "excessively slanted." Whatever your specific needs are, there are plenty of great synonyms available that can help you accurately convey the idea of something being overly favorable or biased.