The antonyms for the phrase "more beside" are less and fewer. While "more beside" indicates an additional amount or quantity, less denotes a smaller amount or quantity. On the other hand, fewer refers to a smaller number of things, people, or objects. For instance, if you say, "I need more books beside me," the antonym for "more" would be "less" or "fewer" if you're talking about the number of books. So, if you're looking to use the opposite of "more beside" in your writing or speech, use "less" or "fewer," depending on the context.