What's the main difference between the phrase "finish [something]" and "finish [something] off?"

Native speaker’s answer
Rebecca
To "finish [something]" means to complete a task or activity. Whereas "finish [something] off" means to finish the task by doing or adding something. "Finish [something] off" can also mean to kill or defeat someone or something, which is usually seen on television. Or it can mean to consume the last of something. Ex: I finished my book off by writing an acknowledgement chapter. => the book was complete by adding a specific chapter. Ex: I finished writing my book. => in general the book is complete Ex: I finished off the brownies. There's no more left. = I had the last of the brownies. There's no more left. Ex: Finish him off. => to kill someone