The antonyms for the word "most itty-bitty" are numerous, and they include "large," "big," "huge," "gigantic," "enormous," "monumental," "jumbo," "mammoth," "colossal," and "titanic." These antonyms connote an immense size or magnitude that is the opposite of "itty-bitty," which means very small or tiny. Other antonyms of "itty-bitty" include "substantial," "significant," "generous," "ample," and "expansive," which indicate a considerable or substantial amount. Therefore, depending on the context and usage, various antonyms can be used to convey ideas that contrast with the meaning of "most itty-bitty.