The natural antonym for "continue ahead" would be to "stop" or "halt." However, other antonyms could include words that indicate a change in direction, such as "turn back," "divert," "veer off," or "deter." Alternatively, antonyms could also indicate a complete opposite action, like "retreat," "retrace," "backtrack," or "reverse course." Antonyms for "continue ahead" could also be more subtle and denote a pause or hesitation, such as "hesitate," "delay," "think twice," or "second-guess." In any case, antonyms for "continue ahead" suggest a deviation or interruption to the original plan, bringing to mind a different path or direction.