If we're talking mirrors...what Bruce could have been if he went the other way with his training/methods, if he went the other way with his business/fortune etc..
Penguin, Black Mask, Bane, Red Hood..
Deathstroke is fine as a character in this movie, since it's a shared universe. But I almost find it insulting that he would be considered for the main villain after The Dark Knight Rises (the last solo) and this could be the ONLY time where they have a chance to deliver a solo Bat film in this universe. And they're going to use Deathstroke as the main antagonist? Like, what? And you're hiring a B or C level actor? It should be an actor with plenty of experience, someone believable. So believable that when you take his mask off and the fighting stops, you know this guy has been through hell. This is awful casting once again, just like Jesse Eisenberg.