The antonyms for "most can-do" are "least able" or "most unable". Can-do refers to a positive, proactive and optimistic approach and attitude, which facilitates successful outcomes. Antonyms for can-do, therefore, convey negative undertones and describe a lack of ability, willingness, or readiness to take on challenges, solve problems, or accomplish goals. Someone who is least able may be prone to pessimism, self-doubt, or inaction. They may lack the necessary skills or resources, or possess a defeatist mentality. Conversely, a most unable person may require assistance, training, or support to increase their capabilities and overcome obstacles.