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.
Crazy Awesome: Lex Luthor's introduction. A top scientist at STAR Labs, he's taking a coffee break playing (and winning) fourteen simultaneous games of chess while reading Machiavelli's The Prince and also listening to a teach-yourself-Urdu tape on a Walkman of his own invention "to keep my mind occupied". He designed and built the walkman only a few hours earlier.
The ultimate example is when Superman implies that the reason he survived Luthor's black hole was that Luthor rounded off a decimal point when calculating Superman's density! See Gambit Roulette on the main page for the full context on this. note It could be argued that since Luthor desired to destroy Superman, not just defeat him, that even in the ending that even though Lex began a Golden Age for all of humanity, Superman surviving just ended up as yet another of his schemes against him. And to bring the point home, Superman literally had the last laugh as he witnessed Lex's funeral, even 2,000 years later. However, Superman despite surviving didn't try to take over the world again, and just lived quietly. In other words, Lex didn't really checkmate him, he just tipped his king piece over and chose to resign.
Luthor's ability to avoid Brainiac's tendrils makes it likely that he planted Brainiac on Superman all of those years ago in order to further his plans.
Superman is oblivious to Pyotr being a traitor to his regime in spite of the latter openly despising him, or Diana clearly being in love with him. This is a hint that this version of Superman doesn't see human beings as people so much as he does as problems that need to be fixed. When Pyotr drunkenly hints that he poisoned Stalin, Superman is too busy solving problems and averting crises to really listen. Lex figures out this flaw and uses it to achieve victory.
Hilarious in Hindsight: In the canon one-shot Superman: The Earth Stealers, a cosmonaut commented that it's a "pity such a magnificent hero did not land in Mother Russia when he came to Earth!"
Magnificent Bastard: Lex Luthor. A formula to fix the US budget, erasing the deficit to non-existence? Arranging a space-satellite crash in Metropolis knowing Superman will definitely show up to save its citizens despite being at war with them? Condemning Lois to a loveless marriage, but knowing full well she'll never leave him? Quadrupling the standard of living of the U.S. and turning it into an economic superpower soon after civil unrest within a year of taking office? And there's that whole Brainiac contingency plan he apparently set up forty years back? To say nothing of the Mary Suetopia he creates after Superman is gone.
Brainiac as well. Everything Superman did was part of his plan all along.
Obvious Judas: Why is Superman so shocked when he finds out from Batman before his suicide that Pyotr betrayed him? He made no secret whatsoever of his hatred of him, and even drunkenly admitted that he poisoned Stalin.
They Wasted a Perfectly Good Plot: A lot of scenes show the canon Superman characters doing random things to show how their lives are different without Superman, even though they have zero connection to the plot. Examples: the Kents, Lois Lane and the Daily Planet staff, etc.
What an Idiot: Pyotr is totally confident of his ability to defeat Batman once their plan to overthrow Superman is complete, right after Bats kidnapped him from his own private car.