Quote Originally Posted by me, just a few posts ago
The wolf isn't Zack. It's the representation of Cloud's feelings of failure, and it appears in places where he feels he has failed someone.

The first place we see it is Zack's grave, so the mistake is understandable. However, the other places it appears have nothing to to with Zack, nor has Zack ever been attached to wolf imagery.

Besides, the creator even said it was Cloud's guilt.
I don't say "The creators say so" lightly. Nomura said it was Cloud's guilt. It is Cloud's guilt.