Mr X has a habit of presumably being killed, but then coming back to life. But who's to say that each Mr X we have seen, is the real one? As Streets Of Rage 3/Bare Knuckle 3 has shown, Mr X CAN make a Robot X duplicate of himself as a decoy if he wants to, and after his defeat at the end of Streets Of Rage 2 we see that his actual body was so badly damaged from before, that the true Mr X was delegated to just a brain in a jar. But yet Mr X was beaten in the aftermath of Streets Of Rage 1, then turned up again completely fine in Streets Of Rage 2. Then it hit me, the Mr X in Streets Of Rage 1 was a Robot X, the one we see in Streets Of Rage 2 was the first true Mr X.
To support that theory, Streets Of Rage Remake features all the levels of SOR 1 and SOR 2, into SOR 1 and SOR 2 routes respectively, within the same game. And while the SOR 1 stage 8 is treated as a good ending, providing you don't purposely try to do the bad ending gimmick, it's actually the SOR 2 stage 8 that's treated as the 'best ending' instead. There is a Robot X route, with remade SOR 3 levels, that upon beating it's stage 8 (same as the Robot X battle in SOR 3 Stage 5) it's quite obviously a 'try again/unfinished' ending given that Mr X is still alive, but it has the same music as the SOR 1 stage 8 ending. I guess the SOR 1 route was still a 'try again/unfinished' route so to speak, but since the game characters believe it really was Mr X, it didn't felt unfinished to them, because they thought it was the good ending. But it was the SOR 1 game's unfinished route, that led to Streets Of Rage 2 having to be a thing in the first place. After the SOR 2 route though, that's it, the real Mr X's body is damaged.
Presumably that's why the remake gives you a choice over which round 5 boat you wish to join, the first game's or the second game's. So you can cross to the right route if you chose to start on the first game's one.
And why the Streets Of Rage 3/Remake routes can actually send you onto the Streets Of Rage 2 route intentionally, but never onto the Streets Of Rage 1 one.
The Streets of Rage Remake has an ingenious difficulty set-up: most of the playable characters are noticeably stronger than their main game counterparts. The game stays fairly balanced, though, as a good chunk of the enemies have lifebars as long as the player's. All of this means that when you play, the game remains fun while still being challenging.
If this doesn't sound so bad, consider that the last three stages involve saving the city from being controlled by the Big Bad and his army of robots who look like high-ranking officials, sparing the Chief of Police (who is to be killed so that his robot double can operate with impunity), and (in the Good ending) disarming the time bombs scattered throughout the city. Now consider a future of the city in which these life-saving actions are never committed...hell, where the plans of the Big Bad are assumed to be prevented already until it's too late, because the characters have defeated Mr. X's clone. Now go back and read the first part again; all of this horror ensues when you pick Easy Mode, and can be prevented if you can beat the game on Normal...which is harder than even the Japanese "Hard" difficulty.