The antonyms for the phrase 'be skillful' include words like unskilled, incompetent, untrained, unschooled, inexpert, and inexperienced. These are the opposite of 'be skillful', which means that they lack the ability or knowledge to perform a task with finesse. Unskilled individuals lack the necessary skills and training to excel in specific areas, while incompetent individuals lack the ability to perform tasks to a reasonably high standard. Being inexpert denotes a lack of knowledge on a particular subject matter, and being inexperienced suggests that someone has not yet had sufficient experience to be regarded as skilled in a particular field. Talentless, clumsy, and amateurish can also be used as antonyms for the phrase 'be skillful,' alluding to individuals who possess no innate ability or are horrendously bad at a particular task.