@AdrianKing There's also the detail that MC is doing all the work of becoming a powerful demon prince, while if the hero succeeds in killing the demon king and the other six, well, he's already said he doesn't care what happens to him after that. So the demon prince can boot the hero at that point and sit on the throne himself.

@Yoman Aku it should be greed but many people consider greed and gluttony too similar ...