The way i killed kerpymon was using kazemon. kazemon can double jump and you can get to kerpymon's head faster than the other digimon. get on top of his head and press or hold "b". this will allow kazemon to deliver multiple kicks to his head. it does some pretty good damage. kazemon is fast and can dodge lightning attacks. always follow kerpymon around. but be careful to dodge his black ball attack. never follow kerpymon to the middle of the screen. he might use his black hole attack. kerpymon might die if you fill up your digivolve meter but only on easy mode.