‘By the time I come’ home is what you are looking for. To make it more threatening, you can say ‘You had better have finished your homework by the time I get home.’!

You can also say: "Finish your homework by the time I've come home" Or: "Finish your homework by the time I arrive home"

Or: "Work on your homework until I come home." Here you aren't telling to finish, but to be busy with the homework until you return.

Hi samar, we do have same desire, please let's practice speaking if you would like to