I see your problem...
BAD END isn't a good thing, it is actuallt the worst thing that could happen to your devilgotchi.
Actually,BAD END only appears if your devil points are too high (95 devil points or higher).If it is too high, he will warn you 5 times-6 times, and then, if you don't lower the DP,he will die.
To lower the DP, you use the angel icon. He gains DP by doing tricks on you, like throwing a pie when he is eating, or he starts to sleep when you are playing the "eat the stars" game. Devil points aren't very good for your tamagotchi, so, the lower the DP,the better character you get.
good luck!