The antonym for the word "un-considered" would be "considered." The word considered means that something has been thought about or taken into account. It is the opposite of un-considered, which means something has not been thought about or ignored. When you consider something, you take the time to reflect and analyze the situation, while un-considered means that something has not been given the proper thought or attention. Using the antonym considered can help to emphasize the importance of taking the time to think about something thoroughly before making a decision or taking action.