Towards the end of episode 48 of Star Crusaders, Dio kicks at Jotaro who uses Star Platinum to punch The World's shin. Star Platinum's fist ends up cracking, but then The World's entire body ends up cracking, killing DIO in the process.
How could this simple punch kill The World?
First of all, you can see that Dio was weakened after he got thrown off of the Road Roller because Jotaro hit his legs.
Second of all Dio mentioned that his left side is weaker than his right side from fusing with Jonathan's body. The leg Star Platinum punched was on his left side too. That's why his body crumbled from the left side upwards.
