Yeah he is hard to kill. A rocket to the mouth freezes him also. The hyper mode is the only way to destroy the balls but once they are destroy things get easier.
LOL lots of people act like they have beaten this game and most of the people that say they are bored couldn't even get past him... So don't give up you are missing a great big chunk of this game if you do. Hold up I'm going to try playing this game with the zapper now! The trigger is welcome and helps.