There are several synonyms for the phrase "be a credit to someone". Some of these include "reflect well on", "do proud", "make someone look good", "enhance someone's reputation", and "improve someone's standing". These phrases all convey the idea of being a positive representation of someone, whether it's through one's actions, behavior, or accomplishments. Being a credit to someone means that one is seen as a valuable asset to that person, and is someone who brings honor and respect to them. It's a way of showing gratitude and appreciation for all the support and guidance they've given, and a sign of one's own dedication and commitment to excellence.