What are they called? Do you mean that kell dragon?
I guess that you really can't kill them easily. In the original, you had to beat one for you to win the level, but in JK, they made them really tough because you don't have to beat them in order to win. I know that they really have a bite in the second game, and they even are harder to kill, but that's just how hard they are to kill in the second game.
I never really fairly won JK because it was like impossible, so I just cheated all the way through.