all you really need to do is hit his third eye with either a charge beam or a missle. he will then roar, and that is your chance to do some same. the is conveniantely a block above you that if you grab onto it is in the perfect tradgectory for firing. however kraid can still throw claws at you. the easiest way, in my opinion is to keep shooting missles at his head, and whenever claws come your way, shoot them and get more missles.