Most paralyzed person in history?

How he looked depended on whether you saw him in the late 90's after the injury or near the end of his life after he had improved considerably. The initial injury was caused by breaking the C1 and C2 bones in his neck... pretty much the same that you would expect if you were hang someone as they do in executions. The only reason he didn't die from it was that the spinal cord inside wasn't severed as it would normally be if you were to hand someone from the gallows. In fact the spinal cord was not cut at all the injury to it came from the hemorrhaging which damaged the spinal cord. Now he received all sort of treatments over the years and apparently some of them worked because he was downgraded from a A level injury (which would be the worst) to a C level shortly before he finally died. That means he had some considerable improvement. Although by most people that improvements were very minor. He could feel sensation on the bottom of one foot and was able to move one finger and the upper part of an arm and control bowel movements. Not huge improvements by a normal person's standard but certain shows signs of progress you would not expect in a C1 or C2 injury.

As for whether no one else had survived such an injury... That's probably not accurate. There have been instances of a person's skull being separated from their spinal cord and the person surviving and returning to a normal life... Is it rare to survive with that type of injury? Yes. And prior to modern medicine it would have killed a person. In fact if you didn't get very quick medical treatment today you would die because C1 and C2 injuries normally affect the ability to breath so you would normally suffocate unless someone hooked you up to a ventilator.

I don't know about history but his injuries were exceptionally severe to the point that he could only move his eyes and mouth and his breathing had to be assisted by electrical stimuli and eventually a machine to do it for him.