The main conflict involves Luigi going out to kill his brother Mario, who has lost almost all control over his body as a result of the boos taking residence in his brain. It really says something when Luigi mentions “holding back” because he can’t immediately bring himself to hurt his sibling, even though expelling the ghosts would only serve to benefit the greater good.
The ending treats us to the painful deaths of Peach and Luigi at Devil Mario’s hands. To add salt to the wound, the boos decide to force Mario back into a state of consciousness in order to observe the damage he inflicted upon Mushroom City and his best friends, unintentionally giving Mario a chance to commit suicide as a means of preventing the boos from annihilating the universe and everything within it.
