We've all known Superman to usually always maintain a cool demeanor even under tough times. But Snyder's Superman is going through a lot in Batman v. Superman: Dawn of Justice which could end up leading him to snap and lose control of himself. Here's what could possibly lead up to him going mad and do more harm than good...
Flashbacks of Zod's death and the Metropolis destruction
Anyone would have nightmares after what happened in Metropolis during Man of Steel. Superman went through a lot during his first day as a superhero, and eventually, in the end had to take a life. In Batman v. Superman hopefully they explore that element of Superman dealing with the trauma of the first film and how it could ultimately change his demeanor and personality. We could possibly see a more aggressive Superman since the events of Man of Steel - does this catch the eye of a certain caped crusader?
The world is against him
The world is split on what to think of Superman. Some think that he is their savior and has come to Earth to save them and help them with their problems, while other think he is a devil and blame him for what happened in Metropolis, citing that if he had never arrived on Earth, Zod and his Kryptonian soldiers wouldn't have come as well. With all that controversy, Superman might become hesitant to help as he might feel unappreciated and angry for basically saving the entire human race and destroying his own in the process without little gratitude.
Batman crusades against him
Batman has a personal vendetta against Superman for causing the destruction in Metropolis. Batman has his eyes set on Superman so he will drive a crusade against destroying Superman as he fears what will become if Superman is left unchecked with all of that power. Superman might not approve of Batman's methods of handling the law and wants to make peace with Batman as he doesn't want a physical confrontation. Sooner or later, Superman will grow tired of Batman's antics and will tell him to stop... or else. Which could end up leading to the big fight.
Superman is going to be under enormous pressure with the government after what happened in Man of Steel. They will likely want Superman to answer for what he did and take responsibility for all the damage and destruction he caused during his battle with General Zod and his Kryptonian soldiers. Superman will likely plead his case, saying that he saved their planet. I have a feeling the government is gonna want Superman to be under their control, even though Superman clearly stated that he would never work for hire. Or knowing the government, they might have more devious plans for our beloved Man of Steel.
Lex Luthor's dog
Lex Luthor could end up making Superman his lackey under certain circumstances. The government and Lex Luthor could be working hand-in-hand and could potentially want Superman to work under them for (yet) unknown reasons. The only way I could see Superman working under anybody is if someone has leverage over him and he is forced to do the bidding of that person. Maybe Lex blackmails Ma Kent - or possibly even Lois Lane. If that ends up happening, that could be the final nail in the coffin and could make Superman really, really mad, potentially making him go rogue for a little while. We'll just have to wait and see until the movie arrives.