"Watch one step" is a common phrase used to warn someone to be careful and aware of their surroundings. Antonyms for this phrase would be "reckless", "carefree", "imprudent", "careless", or "heedless". These words indicate a lack of caution and mindfulness when it comes to walking or moving in general. Alternatively, one could use the phrase "take caution" or "be mindful" as synonyms for "watch one step". These words encourage individuals to act in a more vigilant and careful manner, suggesting a heightened sense of awareness and caution. By encouraging people to take caution and be aware of their movements, one can avoid unnecessary accidents and injuries.