Streets of Rage is a pretty typical side-scrolling beat-em-up. In single-player mode, once you reach the evil Mr. X, he invites you to join his organization. You say hell no, beat him up, then his criminal empire is dissolved and you win the game. But if you reach him with two players, you have the chance to do something very different.
He'll ask you to join him, as per usual. But this time, both players can choose yes or no. If one says yes and the other says no, the two characters will fight. If the one who accepted X's offer wins, X will once again ask if you're truly committed to the cause. This time, say no. Enraged, X and his henchmen will attack you. Stop them, and you'll have won the game. But X's criminal empire won't go away—rather, you'll take it over. A screen will show your character lounging on a throne with text saying, "You became the boss! You are great!" The game then reveals it was lying to you about being great, as after the credits roll, "Bad End" flashes across the screen.
We beg to differ, however. Sure, you had to betray your friend, but now you're the top dog, with an entire, super-powerful criminal regime at your command. That's pretty damn awesome, and you're bound to be better at it than Mr. X was. After all, he's dead and you're not.