I adore scared Dio. I have ever since he was a kid testing the stone mask on randoms. To see him shaken like this made me foam at the mouth, thinking of seeing Dio’s grandiose and confident aura diminish into that little kid once more. Screaming and rejecting the fact that someone can beat him. It didn’t go that far yet, but in the moment of panicked Dio questioning Jotaro if he could really be seen, I got that energy seeping out of him. After thinking he had transcended humanity and surpassed every living thing he was beaten arguably three times by Jonathan. And now, no longer just being a vampire but having a stand that can dominate the world, he finally achieved it, domination over every living thing; what he's been so desperate for. But another stubborn Joestar is here to prove to him that no matter how hard he tries, he can’t reach his ambitions. Yet again Dio’s empty words about killing the descendants quickly was countered by questioning his pride.
We saw his history, testing the World and seeing how it worked. Later Enya takes him under her wing and teaches him how to master it. To move in frozen time, it was integral that he believed that he could do the impossible. Which is honestly amazing because it means that Jotaro can move in frozen time if he believes that he can as well. It means another Joestar can have the will to crush him no matter the advantage he holds. And for Jotaro not to know that explicitly, this means that his desire to kick the hell out of Dio is all the will he needs to defy time. This reminds me of how when writing Dio in Phantom Blood, I'm pretty sure Araki didn't know the solution to his ice powers when he first introduced them making sure the audience didn't either.
Even cooler than all of this, Jotaro’s bluff wasn’t a magnet to scare Dio into giving him some more time. It was a magnet to regain his confidence just in time to shatter a hole in his chest just as Jonathan did to win their fight in Phantom Blood and just like Dio did Kakyoin moments before. A punch through the chest feels right. And most incredible of all, to make Jotaro manly, fearsome, and badass while frozen in time is phenomenal. To have the frozen Joestar staring down Dio and scaring him is like, I can’t properly put words to it. It leaves a freaking strong impression that’s for sure. Not something to soon forget.