Tyson's mental psyche was far weaker than his physical attributes. Had he kept his head on straight, he COULD have been competitive against many of the greatest heavyweight champions who ever lived. I am not saying he would have beaten them all, but would have given them a hell of a fight. For instance, the great Joe Louis, regarded as perhaps the greatest heavyweight champion of all time with 25 successful title defenses of a unified title did have one flaw. This was his chin. If Tyson landed early and Joe was on the floor because of it, could Tyson finish off the great "Brown Bomber?" It's possible. A lot of greats did have vulnerable chins. Foreman proved that Frazier could be put down multiple times and stopped if you got to him early.
BUT Tyson would have to do his "thing" against ANY of the greats early if he was to do them at all. I don't think Tyson could handle the mental pressure of these guys coming back and throwing combinations after Tyson would land his best shots, and these guys just keep coming. In the case of Louis, nobody.......NOBODY kept him down and if these guys could take Tyson's early onslaught and still be there after say 4 rounds, the easier it becomes to beat Tyson. Tyson needed everything going his way to bring out the great physical attributes that he had. Once you get Tyson past the 5th round in a fight where he didn't have things his own way, he would become progressively more beatable. But a prime Tyson, is always competitive against any heavyweight in history for those first four rounds. From 5 to the end, he becomes more ordinary. I think Tyson could go 12 or the old 15 rounds if he had to, but everything would have to be going about 75% his way for him to do that.