No Prep Time
Part 1 Dio: Kenshiro pretty easily, unless Dio managaes to freeze him upon impact or somehow drain his blood, however Kenshiro is too fast and can arguably one shot this Dio, although there could be in argument in this Dio's favor.
Part 3 Dio: Stomps horribly, Dio's Stand was already faster and stronger than Star Platinum who was faster than light and could break diamond hard substances that were as this as houses while under water easily. Not to mention Kenshiro would not even be able to see The World or defend against it since he himself does not have a Stand. On top of that only Homon on conpletely destroying the brain would kill him and Dio by himself was already taking punches to the head from Star Platinum before his final power up. He can also fly for short periods of time since within a few seconds he flew across the city and got a steam roller and carried it back to Jotaro before it past 2 seconds. He may not even need to stop time as he was easily able to deflect Kakyion's Hierophant's Emeral Splash which was shown to be able to destroy multiple massivle building within the town in a single burst with only a flick of his finger. The guy even tanked a train hitting him full on and exploding and he didin't have a scratch on him. However with time stop he stomps even harder as unlike Jotaro, Kenshiro cannot move within the frozen time, and considering that Dio was able to move across entire strets and other great distances when he was able able to stop time for a moment, withi his time stop at 11 seconds with only moments of recovery time he should have no problem one-shotting Kenshiro, he can also stop time near insantly, Jotaro only won that fight because of PIS (Making Dio have to say "Za Warudo" and Jotaro suddenly figuring out that the Stands were the same.)