So Batman v Superman is finally out in theaters and the movie has been getting a lot of negative reviews by critics. I myself have seen the film and like some of those critics I was expecting something more or better. But I digress, some of these critics were pointing to Jesse Eisenberg's Lex Luthor as the culprit for the negative reviews. I am here to tell you that its not Jesse Eisenberg's Lex Luthor that is the problem, but in actuality that he is the solution and as the title suggests, THE MOST IMPORTANT CHARACTER IN THE FILM.
Lets start at the beginning of the film with the battle between Superman and Zod and the destruction of Metropolis and Wayne Tower. Bruce does some awesome driving through the city and finally makes it to the tower only to see it fall. Bruce goes through the wreckage and finds that one of his employees Wallace Keefe (Scoot McNairy) has been injured below his knees.
Somewhere in the Indian Ocean we have many divers searching the wreckage of the Kryptonian World Engine. A couple divers bring in a large piece, where one man who seems to be looking for something takes a hammer and smashes open the Kryptonian piece and a familiar green glow appears before our eyes.
Fast forward 18 months Lois Lane and a fellow reporter are in some war torn country, getting a report on the warlord. We also see that this warlord has private military contractors under his command. Lois goes in for the interview. During the interview, the contractors kill both the soldiers and innocent civilians. Lois is then threatened by the war lord. Superman then comes in and saves her by stopping the warlord.
News about this massacre reaches the United States Government, particularly Senator Finch (Holly Hunter) and the blame goes to superman. They call for superman to stand trial for the actions that he has taken, both good and bad.
In Gotham, Bruce is tracking down a lead which leads to him finding the same contractors and more importantly, who their employer is.
The culmination of these events comes in the form of when Superman arrives for Trial in the Capitol Building in Washington DC. The trial has two sides, Superman on one and Wallace Keefe, who blames Superman for the loss of his legs and his destitution, on the other. Superman arrives at the building where he is listening to the Senator's opening line. We also notice that Lex Luthor, who was supposed to be there, is not present. All of a sudden, an explosion killing all in the courtroom except for Superman. At the same time, cameras all around the world are watching when the horrific event occurs. Not only the world but Bruce as well.
In Gotham, it is only moments before the explosion in the Capitol Building, that Bruce receives strange mail. The mail consists of Uncashed Checks sent to Wallace Keefe, along with Newspaper Clippings about the destruction of Wayne Tower, Metropolis and even some clippings about Batman. Written in large red ink on these documents are various phrases including "You Let Your Family Die!" Wallace Keefe is one of the victims of the Metropolis Event and is standing in as one of the key victims against Superman in the Superman Trial. Then the explosion occurs, and it becomes the last straw for Bruce and prepares to take on Superman.
So how do these events relate to Lex Luthor? Well he is behind it all. Lex Luthor is the employer to these contractors who committed the massacre which eventually forced Superman to go to trial. We also see Lex Luthor manipulate Wallace Keefe, the former Wayne Enterprises Employee by preventing his checks from being cashed for his handicap leading to his destitution, all of this is unbeknownst to Mr. Keefe of course. He is also behind the bombing at the capitol building leading to even more to hate Superman.
But there is more. When Lois was in danger in the war torn country, Superman came to save her yes, well most likely the contractors also witnessed him save her and they simply reported this to Lex. To anyone else, one would think coincidence right. But this is Lex Luthor we're talking about. A manipulative evil genius with a lot of money and resources. He probably questioned why would Superman save Lois Lane, unless Superman was keeping tabs on Lois Lane, and we know for a fact that Lex was closely watching Superman and the actions that he took. He then watched Lois Lane and realized who she was romantically involved with. Which eventually led him to the conclusion that Clark Kent and Superman are the same person.
Now regarding the strange mail that was sent to Bruce Wayne right before the explosion. We know for a fact that the checks weren't cashed by Mr. Keefe. We also see the newspaper clippings and of course the large red lettering. It is either Mr. Keefe or Lex who sent this package to Bruce. If it is indeed Lex, then Lex somehow figured out who Batman's secret identity is. They do not address how Lex figures it out, if at all. But knowing that Lex has kept tabs on a lot of super powered people, including Diana Prince (Wonder Woman), Barry Allen (The Flash), Victor Stone (Cyborg), and Arthur Curry (Aquaman) and not just Superman, he probably also figured out who Batman is.
Now following the events of the explosion, Bruce, who at the this point has figured out that Lex has been secretly searching for Kryptonite, decides to steal the large chunk of Kryptonite as Batman. Batman prepares to fight Superman using the Kryptonite. Lex Luthor sees the carnage left by Batman, and more importantly sees that his Kryptonite is gone and at this point knows who Superman really is, decides to capture Martha Kent which forces Superman to do his bidding. Lex orders Superman to fight and kill Batman, while secretly he hopes Batman kills Superman using the Kryptonite.
All the while Lex has used his access to the wreckage of the Kryptonian ship in Metropolis and from the surviving archives of the wreckage, has learned many Kryptonian Secrets including the abomination known as Doomsday. He even created the abomination using the corpse of General Zod and his own blood. He did this just in case Batman could not kill Superman.
Now if Lex didn't figure Batman's secret identity, then that became the lynch pin in Lex's plan for he did not account for the fact that Bruce and Clark's mothers first names are the same. This same coincidence is also what stops Bruce from killing Clark which eventually leads to the defeat of Doomsday and the arrest of Lex Luthor by all three of them working together.
In the jail scene we realize that Lex knows more than he has led on from the Kryptonian Archives, which has led to many speculation like Brainiac or even Darkseid and Apokolips.
Lex is the main antagonist of the film and has a hand in everything. He created the ruse that Superman is behind the massacre and the bombing. He figures out superman's Identity and possibly Batman's. He knows the identities of the other members of the Justice League. He created Doomsday, and possibly even knows that Brainiac or Darkseid is coming. He has a hand in it all. He is the most important because of the knowledge he possesses and the events that he has created. Whether you liked him or not due to his crazy nature and personality in the film, Jesse Eisenberg's Lex Luthor is the most important character in the film and you should pay attention to his dialogue more than any other character in the film. Except for maybe Bruce Wayne and Barry Allen From the Future.