Syndicate Headquarters is the final stage in Streets of Rage.
This level is the most ambitious and difficult stage in the game for three reasons: the police cannot be called to help the players, every single boss in the game will be faced once again, even in the order they were encountered (by stage) and there are more enemies in this stage compared to the previous ones.
This is also the longest stage in the game, and many rolling trolleys will roll toward the player in which the player can knock them or away, be hit by them or just avoid them. This stage is also different in that the player travels from right to left, not the other way around. As the stage is progressed, the outside will become brighter, as seen through the big windows.
As expected, Mr. X is fought at the end of the stage as the final boss. Once Mr. X is reached, he will ask the player(s) if they want to "be his right hand man". One or both players choosing "yes" will have them fall through the trap door and land back in Stage 6. One player choosing "yes" and the other choosing "no" will cause the players to betray each other and fight to the death, the winning player will be asked the same question as before, this is the only way to get the bad ending if Mr. X is defeated after. If one or both players choose "no", Mr. X will begin fighting the player(s), and defeating him will award the canon good ending.