Antonyms for the phrase "finish off" can include a plethora of words such as "begin," "start," "initiate," "launch," and "commence." These terms indicate the beginning of a process or activity, rather than the end. Another antonym for "finish off" is "prolong," implying a lengthening of the process, rather than a conclusion. Other antonyms may include "pause," "delay," "discontinue," and "postpone," all suggesting a break in the process or activity. Depending on the context, there are many different antonyms for "finish off" that can convey a variety of meanings and implications.