1:
Johnny and the Cobra Kai's are the main antagonists, with them basically coming off like a bunch of high school punk bullies. Kreese isn't really a main antagonist yet, since he is merely their rigid sensei, who always orders them to show no mercy. Johnny, to his credit, gives LaRusso some props when he is defeated in the final match, even if he was the main antagonist whose ass you wanted to see get kicked for most of the movie.
2:
Kreese is briefly shown at the beginning as coming off like a much worse person than he did in the first, but Miyagi quickly takes care of him. The main antagonists become the cartoonish Sato (the way he says, "MIYAGI!", is never not unintentionally hilarious) and his nephew Chosen, who quickly develops a hatred for LaRusso, simply for no other reason than he is Miyagi's friend. Every time there is an exchange between Sato and anyone, he uses that cartoonish angry voice ("DO NOT EMBARRASS UNCLE AGAIN!"), and his death stares were money, if not over the top. Chosen consistently comes off like a tough guy with no redeeming values whatsoever.
3:
The most ridiculous. Kreese returns as one of three antagonists, the other two being Mike Barnes, who is merely a young karate master who wants to kick Daniel's ass cause he thinks he is a joke, and, perhaps the most absurd "villain" ever, Terry Silver. Silver is such a caricature that it is always impossible to take him seriously as a character you should hate. That scene in the dojo where Silver and Kreese are laughing like villains in silent movies is one of the most ridiculous things I've ever seen. I wonder if that was actually in the script that way, or did the actors just go over the top with their laughing?
Thing is, Kreese does a good job as antagonist otherwise, always having that steely stare that could cut through you, but Silver always had that swarmy grin, when combined with his laughing, made him more comical (in a bad way) than anything.