Bare Knuckle

Press Left,Left,B,B,B,C,C,C, Start at the title screen.

When you get to the final boss playing 2-player mode, have one player choose ''yes'' and the other choose ''no''. You will be forced to duel against each other.

Go to the main menu. Hold down (A) + (B) + (C) + RIGHT on controller 2 while selecting Options on controller 1 (best if done with two people). You can now select how many lives you start with and which stage to start on.

To get the Bad Ending, you must be playing as 2 players. You must also be in 2 player mode before Level 8 or else player 2 can't come into the game on Level 8. When both players reach Mr. X in the final room and he asks his question, make sure one player answers yes and the second answers no. Mr. X will have both players fight each other to the death. Have one player lose and choose game over. Afterwards, Mr. X will ask a second question. Be sure to answer NO to that question as well to trigger the final boss battle. When you beat him, you will become the Boss. NOTE: If you answer yes, you will again be shut back 2 levels and still not be ale to get the bad ending.