When we say someone "took the bull by the horns," we mean that they confronted a problem or challenge head-on, and dealt with it boldly and decisively. The opposite of this phrase would be cowardly, evasive, or timid behavior in the face of adversity. Some antonyms for "took the bull by the horns" might include avoiding confrontation, shying away from difficult tasks, or hesitating to take action when needed. Conversely, those who embody the spirit of "taking the bull by the horns" may be described using words such as brave, courageous, determined, or proactive.