These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: The story features several of DC's worst, with appearances from Mister Mind, The Joker, Gorilla Grodd, Vandal Savage, and Brainiac. And while Mind and Joker don't get up to that much villainy in-story, Grodd, Savage, and Brainiac are all in fine evil form, leaving considerable bodycounts in their wake. See the appropriate pages for more on them.
Magnificent Bastard: Luthor reconfirms his position as the DC Universe's biggest MB in this arc, as he outwits fellow evil geniuses Mister Mind, Brainiac, and Vandal Savage to claim his place at the very top of DC's villainous hierarchy, incorporating all of their schemes into his own, and predicting everything down to the last detail. In the end, only Luthor's own ego and inability to let go of the past can bring him down.
Moral Event Horizon: Luthor crossed it years ago, but one could argue that within this arc itself he crosses it when he throws away a chance to heal all the pain in the universe just for one last shot at killing Superman. It's certainly at this point that the narrative abandons him.
The finale. Lex Luthor, having gained the power of a god decides it's time to finally kill Superman and summons him into space for a final showdown, during which he learns that Superman is Clark Kent... and promptly LOSES IT, raging at the perceived injustice that Superman got to have parents like the Kents, while he had a scumbag like Lionel for a father. In the end, he has the choice to bring peace and happiness to the universe FOREVER... or kill Superman. And he just can't do it. He finally loses his mind as he realizes everything he's lost, not even knowing his own name.
It's not just that. Luthor, with the power of a god, decides to torment Superman with visons of loss, as he believes that Superman is so alien that he couldn't understand the concept. First he shows Superman how much pain the citizens of Metropolis felt when he was murdered by Doomsday, then showing his birth parents' final moments on a dying Krypton, then his loss of the person he called his son, Chris Kent (Lor-Zod) as he threw himself into the Phantom Zone to stop his bastard of a father General Zod and finally the destruction of New Krypton. Yelling at Luthor to materialize the most painful loss in his life, Luthor then shows the death of Jonathan Kent in Clark and Martha's arms. The realization that dawns upon Luthor is surprisingly painful.
In a certain way, even Grodd is pitiful. When Luthor's bliss reaches him, he's paralyzed by it, wondering if he's ill. He's never experienced real happiness before.