Nobody ever uses right alt even if it exists, but it's straightforward to hit F4 with your right hand.

Alt+F4 on Windows has the undesirable property that if you hit it several times, and it works, you'll close several different things. Ctrl-C in the terminal won't do this.

American Emacs-using touch typists use right ALT all the time. ALT-x prompts you for a command, ALT-q in most modes runs fill-paragraph, ALT-f moves the cursor forward by one word, etc.