From Longman Dictionary of Contemporary Englishat bestat bestJUST/ALMOST NOTused to emphasize that something is not very good, pleasant, honest etc even if you consider it in the best possible way The campaign was at best only partially successful. The technique is at best ineffective and at worst dangerous. → best
Examples from the Corpus
at best• At best, sales have been good but not great.• Public transportation is at best limited.From Longman Business Dictionaryat bestat ˈbest adverb FINANCE if someone buys or sells a SECURITY at best, they buy or sell it at the most profitable price available → compare limit order 