Please help, Looking for the name of an old Sci-Fi Movie

Hello everyone, I recently lost my father and Was reminiscing about things we used to do together when I was a young child. I distinctly remember an old sci-fi movie that I watched with him as a young child. This sci-fi movie has two men in it that somehow in a scientific experience become large giants. From the very best of my recollection I remember the two giant men were somehow related to each other and one of them became evil and one of them was good. There’s two giant men throughout the movie fight each other. I believe the movie is in black-and-white and the two men were represented by two different colors of the hair. From my recollection I believe the movie was done in black-and-white but it may have been in color I just simply can’t remember because I was very young. I am 57 now, and I would really like to watch this very old sci-fi movie again reminiscing about my father! I have searched and searched on google, but I cannot find the title of this movie. Your help would greatly be appreciated!! Thank You!!