I`d say it`s between Seldon, Stewart, Spinks or Bruno (rematch) which one was the most petrified of fighting Tyson?
Spinks fought a better fight than most give him credit for. I'd say Bruce Seldon. Dude shook his head to clear the cobwebs but THAT ended up knocking him out?! After that is Alex Stewart. Both KO's were frightening...
I think James Bonecrusher Smith in 1987, remember they called it The Bone Hugger Fight, and of course Michael Spinks in 1988, he sure did look scared. It did not last very long the way Michael got brutalized.