So who do you think is the most powerful character?


That's kinda funny cause it's physically almost impossible to kill him....
“God is dead. God remains dead. And we have killed him. How shall we comfort ourselves, the murderers of all murderers? What was holiest and mightiest of all that the world has yet owned has bled to death under our knives: who will wipe this blood off us? What water is there for us to clean ourselves? What festivals of atonement, what sacred games shall we have to invent? Is not the greatness of this deed too great for us? Must we ourselves not become gods simply to appear worthy of it?” - The Gay Science, Section 125, The Madman, Nietzsche.
Not only that,remember how Madoka was dethroned by himura when she was onipotent, a truly goddess (the whole madoka magica has A LOT of nietzsche references about it and also the ubermensch and nihilism
Some of the JoJo characters have their powers defined in a very loose way, so their power levels could be interpreted to be impossibly high.
For instance, Giorno Giovanna could be interpreted as having a Stand that will prevent anything bad from happening to him, causing time to go backwards just to deny events. It's unclear whether he needs to be conscious of what's happening in order to act, what his range is (infinite?) or whether he can be caught unaware by anything at all.
He could possibly prevent absolutely anything time or space-related as long as it's detrimental to him, with no limit whatsoever.
I don't know whether by using the term Powerful, you mean only the physical aspect or otherwise.
But if i were to assume by overall, i would go for Lelouch Lamperouge.
though he had this supernatural power, but he was a genius in strategics and tactics (Specially in anime version of story). So much that he literally made the world dance to his tune to achieve his goal.
If i want to go for a physically strong person without any superpowers maybe, i would shoot for Shizuo Heiwajima.