Shinra really is a fantastic antagonist conceptually. I'd say they were a fantastic antagonist in general, but it's been forever since I've played all of VII and can't remember how well it was pulled off. I do now kind of wish that Sephiroth had a lot less screen time though. Not that he had that much, but I did really like the opening stuff as you mentioned, Psychotic. There's something really menacing and exciting about an antagonist when you just keep seeing the aftermath but rarely if ever actually seeing the person that caused it.