KK really needs a better name.
I remember this mostly by how the cartoon played out. Karate Kid joins on a recommendation from superboyman, but gets little respect from the other legionares because he doesn't have any powers. A guy called Nemises Kid joins at the same time, who's power is to take other people's powers away.
I'm sure you see where this is going, right?
...well you're wrong, as the story's big bad has nothing at all to do with Nemesis Kid, and when Karate Kid inevitably beats said big bad and proves his worth, Nemesis is one of the Legionares who thanks him and apologizes for his earlier behavior.
It was just one of the many ways the series loved playing with your expectations.