Theoretically, Kars has 400 IQ, but he acted very irrational.
Dio? Well... he has one of the most powerful power in JoJo - time stop. If he wasn't cocky, he could easily kill Joestar group at the moment when they entered to his mansion.
Kira? Hmmm.... I think he is most consistent villain. He very well used Killer Queen powers (fight with Josuke). Of course, he suffer on typical main villain sickness - he is extremaly cocky, and due this, he said everything about himself to Hayato.
I don't know Diavolo and others, so I don't judge them.
Probably Funny Valentine, he literally commits no mistakes.
But all the villains are brilliant in their own ways though, if not Valentine it'd be a toss up between Dio and Diavolo. They were consistently outsmarting the jojos but had a fair deal of luck though. Their cockiness ultimately didn't affect their battles much.
Only Kira really entered the realm of committing a dumbass mistake that actually cost him victory.
Kars, and not just because of his IQ of 400. Remember his fight against Lisa Lisa and Joseph? Yeah, that speaks for itself, really. If not for Stroheim's intervention and icredible, dumb luck on Josephs part, Kars would have obtained the ultimate victory.
yeah i gotta agree with diavolo he's one cautiouse mf and only lost in the end cause of GER XD but yeah with his efficient use of both time-skip and epitaph he was as was said before able to avoid all contact with anyone (e.g. cleaning the room before the lady walked in clearing all proof of him being there) and also how he will use epitaph to see if thing's will go his way and if not will move accordingly to counter anything that came his way, he also manipulated certain situations suchas the riscotto fight to help him without doing much.
Agreed. The only reason Diavolo lost was cuz of deus ex machina and how Giorno got GER. If the concept of Deus Ex Machina never came into play, Giorno would have a little bit more of a struggle against Diavolo. His chances of winning couldve been little to none with Diavolo's ability to basically timeskip against Giorno's ability to spring forth life
And he would have learned from his mistake and would think differently in the future. Bruno had already been donuted and chopped. I’d be feeling pretty cocky too if my opponent was in that condition. I’ll admit that Diavolo has made some pretty stupid choices like deciding not to flee. He sent a bunch of his own elite guard after team bucciarati and none of them or la Squadra could kill any of them. All of the members in team bucciarati who died were all killed by Diavolo himself. He could have handled them himself if he decided not to hide for most of the part.