out of all the people you could've chosen to give Bob the slightest of chances you picked the ****ing muderer's row
IMO, the closest thing he'd have to even the faintest semblance of a chance would be Frazier, for no other reason than Frazier would likely come to him & (at least in theory) that was the style of opponent he most excelled against.
Of the choices given (for the reason Bolo Specialist states), I agree Joe Frazier is the one Bob Fitzsimmons has the best chance against, and that heavily depends on which version of each fighter appears in the ring.
Frazier. Any tough, good banger could beat Frazier... if it was Fitz in the place of Bonavena, he would have stopped Joe.. easy to see it. Liston´s reach was a tough task but Fitz would have a shot... Foreman and Wlad ? No. They beat him...
They all knock him out. BTW he has no chance whatsoever against Frazier. I find it comical to think he does