Polish? Works wonders for tarnished metal.
...Anyway, about the other main characters... I doubt they're dead. Sure, Cloud's all alone, but then he went through countless traumatic experiences, got used for experiements and drugged for years, lost his family and friends, killed hundreds of people, then finally settled the score and saved the world. A bit too much pressure there, I think. It'd be enough to mess anyone up and turn them a bit antisocial.