Suicide Squad: Kill the Justice League has revealed a good amount of characters in the game, but the biggest, most obvious name that hasn't come up yet is Lex Luthor. As one of DC's biggest villains, it would already make sense for him to show up - especially with a mind-controlled Superman on the loose. When taking his history into account, it would make perfect sense for him to take a major role.
Lex Luthor is Superman's most famous nemesis. He may not be the most powerful, having no superpowers of his own, but he is the most enduring. A scientific genius and successful businessman, he is powerful in every sense aside from physical strength as far as basic human standards go. If Suicide Squad hasn't shown all of its villains, then Lex should be among their number for sure. His rivalry with Superman is fueled largely by his own ego, since no matter how successful he is, Superman's powers and universal respect are something he can never attain. Lex's pettiness and thirst for power have led this to become one of the greatest rivalries in comic books.
Lex Luthor Is Superman's Perfect Opponent For Suicide Squad: KTJL
Since Suicide Squad: Kill the Justice League features an evil version of Superman, it would only make sense for Lex to make an appearance. Not only would this be yet another opportunity for him to fight Superman, but at least to him, it would validate his continual distrust of the hero. Possibly due to his resentment, Lex refuses to believe that Superman could be simply good. While Brainiac is the perfect villain for Suicide Squad, Lex is the perfect opponent for Superman. Not only would seeing an evil Superman make Lex feel like he was in the right, but he would also jump at the chance to stop him so that he could be revered as a hero.
Lex has more than his hatred of Superman to work off of, though. Although he may be one of the physically weakest foes that the Man of Steel has faced (at least without his power suit), Lex is one of the smartest supervillains in the DC Universe. There's a reason why, in many of DC's supervillain team-ups, Lex has a tendency to be the brains of the operation. Similar to how KTJL could show why DC's heroes need Batman as a leader and strategist, Lex could appear and put a twisted spin on that role. While the Task Force X already has Amanda Waller leading them in Suicide Squad: Kill the Justice League, Lex's battle suit could let him issue commands in the field rather than from afar.
One big point in Lex's favor is that he has previous experience with similar situations. In the Forever Evil event, Lex spearheaded the resistance against the Crime Syndicate, an evil version of the Justice League from an alternate universe. In addition to giving Lex a chance to show off his more admirable qualities, Lex is indispensable in this arc, being the one to ultimately save the day and finish the battle. With the evil Justice League in Suicide Squad: Kill the Justice League bringing back memories of Forever Evil, it would make sense if Lex took a stand there as well. Suicide Squad: KTJL can learn from DC's films, but Forever Evil may be a better source to take inspiration from.
There's no word on whether Lex Luthor will be in KTJL, and he may end up not being in the game at all. However, given how much of a history Lex has with the Justice League and Superman in particular, a chance to face an evil Man of Steel is too good to waste. Suicide Squad: Kill the Justice League could benefit greatly from Lex's presence.
Source: DC/YouTube