Batman v Superman: Dawn of Justice's main brawl was between DC's Man of Steel and Dark Knight, but the two heroes later set aside their beef with one another and teamed up with Wonder Woman to battle Doomsday. Created by Lex Luthor by merging his blood with General Zod's corpse in the Genesis Chamber, this "Kryptonian Deformity" was just as dangerous as his comic book counterpart, and it was only defeated when Superman sacrificed himself. Fast-forward to Justice League, one fan has noticed that Kal-El's arrival at the damaged Superman statue in Metropolis matches up with when Doomsday came to the landmark in Batman v Superman, as you'll see below.
Both Batman v Superman: Dawn of Justice and Justice League were directed by Zack Snyder, and given the remarkable similarities seen in this video posted by Twitter user JNapierrr, it's hard to imagine this was just a happy coincidence on Snyder's part. Both Doomsday and Superman arrive at the Superman statue in a similar way (though the former's entrance is more graceful than the latter's), and then they both turn around to face who they'll be fighting soon. For Doomsday, that was Superman, and for the recently-resurrected Last Son of Krypton in Justice League, that was Wonder Woman, Aquaman, Flash and Cyborg. It's a nice thematic callback, especially with Superman being moody and violent at this point in Justice League, much like Doomsday's natural state.
Just like in the comics, we have Doomsday to thank for Superman's death in the DC Extended Universe. With the monstrous creature growing more powerful than Superman and Wonder Woman combined, Batman realized that the only way to defeat it was to take advantage of its shared weakness to kryptonite, leading Superman to grab Batman's kryptonite spear and impale Doomsday with it. Superman died carrying out that noble act, but a year later, he was brought back to life by the newly-formed Justice League to help them defeat Steppenwolf. What they didn't count on was the Man of Steel not having his memories back, and when Cyborg accidentally launched a projectile at him, that sent the Kryptonian into rage mode. If Batman hadn't brought Lois Lane to the battle, you can bet Superman would have killed all the other heroes, and who knows what he might he done to the rest of Metropolis. Fortunately, he calmed down following a trip to goo ol' Smallville, and after acquiring a new costume, he flew off to Russia and helped save the day.