im still not totaly sure how i exactly beat it but what i did was jumping on his big ball(this sounds strange O.o)because it was so elastic so i thought this must have a reason^^ and then i kicked it from behind. And i ever used the freeze. But im not sure if it fell to the back when i kicked it and i had to jump on it or if i had to kick it again. Try it out but the back is the weak point i think