The antonym for "more frictionless" would be "more cumbersome" or "more difficult." When something is "more frictionless," it implies that it moves more easily and smoothly, without any obstacles or problems. But if something is "more cumbersome," it suggests that it is heavy, unwieldy, or awkward to move, and it may require more effort to get it going. Similarly, if something is "more difficult," it means that it is more challenging or complicated, and it may be harder to achieve the desired result. Therefore, it's important to pay attention to the context and choose the right antonym based on the intended meaning.