There are two ways to kill the Dr. Willy level 4 Boss. One way is to use Clash/Crashman's weapon on the walls and the Boss, but you will not have enough left to defeat the Boss (you must keep getting hit and die). When you start back at the check point, find some more weapon energy to fill up Clash/Crashman's weapon. Return to the Boss. The ones you destroyed are gone, but the walls will remain. You now should be able to defeat the Boss. The other way is make sure you have some #1 and #3 remaining. Use #1 to fly up, shoot the one on the right, jump down, shoot that one, use #3 on the wall, go up, head to the bottom right, use one on the wall and the Boss, shoot the ones on the left, then use #1 and fly up. Use the last bit of energy remaining on the last one.