Antonyms for "most overventuresome" can be words that describe someone who is cautious, careful, or reserved. These could include words such as prudent, wary, guarded, timid, shy, or reserved. A person who is most overventuresome is someone who takes risks without considering the consequences, so antonyms would be words that describe someone who thinks before acting. Such people may be more methodical, analytical, or conscientious in their approach to decision-making. Antonyms for this phrase could include words like thoughtful, deliberate, considerate, or contemplative. Ultimately, the opposite of being most overventuresome is to act with prudence and to carefully consider potential risks and benefits before making decisions.