Well, he wasn't actuall on-screen, and he's not even my favorite villan. But when Cloud woke up in that Shinra cell. and there were bloodstains on the wall, I was slightly afraid what was going to happen next. I imagined his massacring the Shinra employees and ending up in the president's office. If that doesn't count, then I like Sin's entrance. He just seems so ominous as he destroys the city of Zanarkand.
