If you are determined to see a movie where a movie star fights himself, let me recommend 1991's "Double Impact"; the tagline is "Double the Van Dammage!" and does not disappoint. Hey, it is what it aims to be, which cannot be said for "Gemini Man."
Google: "NBC News Everyone Knew Lauer "Like most movies today, despite the presence of Mary Elizabeth Winstead, Gemini Man is as sexless as Mr. Rogers. As if this movie isn’t frustrating enough, we don’t even get a decent look at her during a strip search. What the hell, Hollywood?"