Canon Superman beats down Superboy-Prime in a last slugfest without powers, saying that "It's not about where you're from. It's about what you do. It's about action."
Superboy Prime himself. He took a punch from Black Adam and it only tickled him and then punched him away like he was nothing, killed a bunch of characters and who knows how many GLs, and even after having his powers taken away beat the older Superman from Earth-Two to death and nearly beat the younger Superman as well. In fact he would have killed the younger had Earth-Two Superman not stopped him.
The Joker gets his revenge for being left out of the Secret Society by giving Alexander Luthor two shotgun shells to the head.
Lex Luthor: Oh, Alex. You made a lot of mistakes. You underestimated Superman. Superboy. Me. But the biggest one? You didnít let the Joker play.
What does it say about how dangerous Joker is when Lex Luthor of all people admitted that excluding Joker was a bigger mistake than anyone underestimating himself?
Wonder Woman talking down Batman from shooting Alexander Luthor. It shows not only her character development, but Batman's, choosing to be the better person rather than give into Alex's claims about the universe. He also preserves his morals.
Debatably, Diana underwent no character-development at all; her killing Max Lord was due to the fact that there was no other way to break his mind-control of Superman. With Alexander, there was no pressing need to kill him.
Batman is talked down from killing Alexander Luthor, preserving his morals and proving he's not as evil or broken as Alex thinks. The next time Batman picks up a gun is in Final Crisis, if only to try to literally save the multiverse from the black hole of evil that Darkseid had become.
Superboy (Kon-El, the clone) fights it out with Superboy Prime. Kon-El is explicitly weaker than Superman, and has partly-human DNA. Superboy Prime is explicitly still at his pre-Crisis strength, making him still stronger than Superman. Kon-El keeps his priorities straight during the fight against a massively more powerful foe that's easily taunted, and as a result, Kon-El saves the world even as he loses the fight, cementing his Dying Moment of Awesome.
Earlier, Kon-El and Superboy Prime were slugging it out in downtown Smallville, with Conner clearly on the losing side of the fight. Krypto leapt in to defend his master, managing to bite Prime before he gets punted down the street. Cue Kon-El rising from the rubble, eyes glowing red and pissed off that someone hurt his dog.
After being released from his confinement, Martian Manhunter takes on Superboy-Prime, and managed to hold his own for a few moments, including phasing through blast of Prime's heat vision.
"I do not know who you are. But I am called Martian Manhunter. I am Mars' sole survivor. There is a reason for that."
Alexander Luthor's collecting remnants of the Multiverse of old, and using a design base on one of the Anti-Monitor's universe-destroying machines to recreate the Multiverse. What does Alexander Luthor use as fuel? The Anti-Monitor's corpse.
When the Superman of Earth-2 berates the Earth-1 heroes for not measuring up to the standard that his heroes originally set, Earth-1 Superman gives this reply:
"If you're from this Earth, it can't be perfect. Because a perfect Earth doesn't need a Superman."