The phrase "doctoring up" is often used to describe the act of improving or enhancing something, sometimes with deceitful intent. However, there are several antonyms that convey the opposite meaning, such as "ruining," "destroying," "spoiling" or "worsening." These words suggest that an action is not meant to improve something; instead, it is intended to worsen it. Other antonyms for "doctoring up" could be "neglecting," "ignoring," or "abandoning," indicating a lack of attention or care towards something. Ultimately, the choice of antonym for "doctoring up" depends on the specific context and intention of the action being described.