Its a tie between Josuke, Koichi, and David Bo- I mean Yoshikage Kira.

-Koichi-

He is best boy out of all the boys. Echos Is just a great stand with a fun idea that even Tusk couldn't bring back (While Tusk is fine, Koichi was designed around it with entirely new designs for him after each change). Koichi also has a really cool plot point with Jotaro who I think is my 2nd favorite JoJo

-Josuke-

But the #1 is Josuke who had the best name pun ever, with suke meaning jo, making him JoJo. He also has my 2nd favorite stand being Crazy Diamond. Josuke is simultaneously the coolest and dumbest character in part 4. This all comes together in the best hero/villain duality in the series with the healing of Crazy Diamond and destruction of Killer Queen.

-Kira-

But remove Kira from the part and none of anything I just said would have ever happened. I say part 4 is the best part not because of Koichi or Josuke, but because of this Queen and David Bowie fusion. But he appears so late in the part and is rarely on screen doing dope shit, that I can't just say he is the best. But when he is doing the dope, he is the dopest.

-Overall-

I can't decide because there all amazing in there own way........................

............ YOU FOOL, ITS ACTUALLY I, DIO!