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.
Asspull: The Justice League of America once went up against Despero (an alien with vast mental powers, at the time recently powered-up to be almost as strong and invulnerable as Superman) with a mostly C-List team. How to beat him? With an innate Martian power that the Martian Manhunter had never before mentioned that he had, because using it was so stressful that any given Martian can only do it once in their life. Despite that, it was still a fairly well-received story. Another weird power of his was the ability to see through the flow of time. This somehow resulted in him being immune to the powers of an opponent who completely rewrote reality. Pulling never before seen powers out of his ass is the Martian Manhunter's shtick. And then getting lit on fire the next time said power would have been useful.
Complete Monster: Felix Faust is one of the most power hungry sorcerers alive. Kicking off his career by selling his infant son's soul for his own ability, Faust committed many acts of cruel murder and torture to fuel his black magic. When he finally realized he could no longer bargain with his own tainted soul, Faust resorted to harvesting the soul of an innocent little girl to trade to demons. Faust offered his assistance to Black Adam to help resurrect Black Adam's wife Isis, but deceived Adam into thinking Isis's revival had failed, while Faust kept a paralyzed Isis to serve as his personal sex toy.
Crowning Moment of Heartwarming: V1, #158. By this point, Red Tornado (who happens to be an android,) has been a member of the group for a while, but still has doubts about both himself, and his relationships with his other teammates. There are times when he isn't sure if his teammates truly trust him; where he wonders if all they think of him is just some machine. In this issue, that matter is solved once and for all. After Red Tornado contains a freaking explosion, he briefly falls unconscious, and drops into the sea below. He probably could have flown out shortly after, but Batman, after dealing with other matters, flies back to Reddy in his jet, and pulls him out of the drink with a rope. As he's climbing, we get this:
Red Tornado: "But... how could you find me, out here...?
Batman: "How do you think? I followed you in my Batplane! A Justice Leaguer doesn't desert his friends, Reddy!"
Red Tornado:"Am I... your friend?''"
Batman: *Batman, of all people, simply clasps Reddy's hand, and smiles; Reddy smiles in turn.*
Ensemble Darkhorse: Tomorrow Woman of Grant Morrison's run on JLA. Originally debuting and making a Heroic Sacrifice in the same issue, she was so popular she reappeared in a special one-shot dedicated to her, was briefly brought back in Hourman #2 by the main character, and then was brought back in Trinity, where she was permanently revived as a human woman with superpowers after the series ended.
Fridge Horror: JLA: Rock of Ages showed a possible future where Darkseid ruled. Darkseid had a scar on the right side of his face in that future and his jawline was more pronounced. In JLA: World War III General Eiling says that he is "the face of tomorrow". Note that he had red eyes, a lantern jaw and a scar on the right side of his face. Now take into account Final Crisis, where Darkseid manages to cheat death by hiding in human hosts...
Memetic Sex God: Dale Gunn, a bald, middle-aged, unpowered mechanic who inexplicably had both Zatanna and Vixen after him in the Detroit era.
Take That, Scrappy!: Vibe and Steel from the reviled Justice League Detroit were killed off several years after they were created due to negative fan reaction. Decades after their deaths, the characters are almost never mentioned in-universe unless in a negative manner.
This itself got lampshaded when Black Lantern versions confronted the surviving Detroit Leaguers and basically asked why they were remembered as jokes while their teammates, Gypsy and Vixen, got to join the "real" League.