The term "most well-proportioned" refers to something that is very balanced and harmonious in its design, shape or form. However, the antonyms of this phrase could be "disproportionate", "lopsided" or "uneven" which convey a sense of irregularity, asymmetry, or lack of symmetry in the object or subject. "Awkward" and "clumsy" are also antonyms of "most well-proportioned" as they denote something that is unrefined, ungraceful or poorly designed. Conversely, "unbalanced", "imperfect" and "jagged" are other antonyms that show a lack of harmony, order, or coherence.