Quote Originally Posted by Ergroilnin View Post
(and he attacked it only thanks to Jecht, to what extent it was Sin and Jecht that actually destroyed half of the city, who knows)
We know that Jecht as no will and intention to destroy cities as he is no bad person and "when he cannot control himself" that is not him (in terms of his consciousness and will) but Sin (you could say similiar to JENOVA in Final Fantasy VII which is also an instinctive being and only one person actually was fully able to control what lived of it in him). Sin is a part of Jecht, so the instinctive part and so basically the "Sin is Jecht" is true of course that is true but those are instincts he does not want with his consciousness and so he controls them. He cannot though and so he at least shows Tidus that he has to end it. That also means, while Sin with Jecht in control was swimming to Zanarkand it was not Jecht (as you might notice I always say "Jecht" when I talk about the conscious person which is right) who actually destroyed it as Jecht himself does not accept that urge to destroy as a part of his body and so the animal itself breaks through without him. I think you very well know Jecht is not a bad person and that was surely not your point. I just point it out to show you that the person that Jecht is, self-aware and conscious of his own Self would never do that. He visits Tidus with the thought of "look what happens when you don't stop Sin" and that means as long as he intends to go to Tidus he is to blame a bit but while it was his intention to prove Sin is not good for Spira it also shows that he actually did not do it. It is a part he cannot resist and it will kill Jecht himself eventually to only leave Sin itself behind. That threat was the very reason to stop him. People being lucky that Sin didn't attack some cities is no guarantee that this would go on forever as Sin itself does no longer just act as intended by Yevon.

Quote Originally Posted by Ergroilnin View Post
It's also obvious enough that Sin normally isn't so aggresive, it doesn't even really attack Bevelle and Luca, if crusaders can protect those cities, the Sin isn't really trying. It probably just swims in the endless seas for the most time being relatively harmless.

Since Sin been around for so long and been dead so little yet the Spira is still around, even if there was no way to kill it, it would be as you called it, more like force of a nature, you can't really kill tsunami or hurricane and they kill and destroy cities as well.

So really without Seymours intent to kill all Spira with Sin, it wouldn't really matter that much.
That still sounds to be like the bee comparison. Sin is okay and no problem as long as no one acts - but that isn't true. It was an incalculable threat and Jecht knew that which was why he said he will think about something to finally destroy it in the first place as an unleashed Sin cannot be lived with without being scared of that fore suddenly appearing and ending your life. A force of nature is a bit more than just something to be provoked (Sin still is provoked, I do not disagree here, I just say Sin is more).