The common phrase "not lift a finger" means to do nothing or not make any effort towards a task. Antonyms for this phrase include exerting effort, working diligently, being proactive, taking the initiative, or completing the task promptly. One could also use specific action words that describe the opposite of inaction like mobilizing, executing, engaging, or accomplishing. Another antonym for "not lift a finger" is to be productive or efficient, such as being proactive in getting things done rather than leaving work for others. In short, if you want to find the opposite of "not lift a finger," you need to look for words that describe the opposite of inactivity and procrastination.