The term 'most close-by' implies an object or location that is closest to a particular point. Antonyms for this term could include words such as 'farthest,' 'distant,' 'remote,' 'removed,' 'far-off,' or 'faraway.' These words connote distance, separation or isolation, whereas 'most close-by' is a word that describes proximity or adjacency. Other antonyms could include 'furthest,' 'aloof,' 'detached,' 'unreachable' or even 'unapproachable.' Using an antonym to provide a contrasting meaning to a word can help to clarify its meaning and provide additional emphasis in writing or speech.