10. Red Hood
Jason Todd, aka the Robin that died (well, the first Robin to die) was resurrected and became a violent vigilante with grudge against Batman. Yes, Injustice is already pretty Batman-heavy when it comes to the characters in the game but this one just makes so much sense. The dark and gritty feel of the game, the heroes turning against each other, the visceral displays of violence. Everything about Injustice lends itself to the ethos of one Jason Todd. He also has the look that fits so well into the games presentation. He already has a serious grudge against the Joker (and who wouldnt if they were him?) due to being beaten to death with a crowbar, but as the events of Under The Hood showed he also is pretty pissed off with Batman for continuing to let the Joker live. This would set him up perfectly to join Supermans side and further his disdain with Batman.