Sephiroth, normal, Rebirth or Sepher would choose all of them at once which he did anyway by demonstrating how powerless they are in his presence.

If I must choose though:

Cloud - because of the grudge which was the reason to go for him
Vincent - because, knowing of the Lifestream and reading minds, he knows of all the background, also to hurt Cloud
For the last one he rolls. Everyone of them being hurt would hurt Cloud anyway.