Functionalize is a verb that means to make functional or useful. Some antonyms of functionalize are: malfunction, disable, break down, destroy, render useless, disenable, incapacitate, inactivate, and impair. Malfunction refers to a failure to work or operate correctly, whereas disable involves the process of making something ineffective or unusable. To destroy is to ruin completely or bring to an end, while render useless involves the process of making something or someone futile. Disenable is the opposite of enable, meaning to make something difficult or impossible to do, while incapacitate refers to the process of making someone unable to perform their duties or activities. Inactivate means to make something non-active or non-functional, while impair involves the process of damaging or weakening something.