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.
Prior to the release of Blackest Night #0, it was established in Nightwing that there was a black market for metahuman bodies and organs, leading to the League's confiscation of them. At the end of BL #0, there is a shot of the Black Lantern Corps with its members rising from a graveyard, with no indication that this was to actually happen. The Internet Backdraft was substantial, saying that DC was ignoring what the Nightwing writer, Peter Tomasi, had established; but it turned out to be the opposite as BL #1 made direct reference to the Nightwing storyline. This made it all the more sillier since Tomasi had been writing for the monthly Green Lantern Corps book for at least two years previous... and what was supposed to be a non-canon group picture of the Black Lantern Corps was taken literally.
And then there's the origins of the entities shown in Green Lantern #52. The only explicit stuff is that the avarice entity is a serpent and discussed while showing a snake and an apple, and the hope entity was said to be born from prayer; but of course it's prompted Wild Mass Guessing as to what other religious symbolism can be inferred about the entities. The fact that the story also makes reference to "Let there be light" doesn't help.
Internet Backdraft: Fans of the Titans were not happy that Tempest was used as a Sacrificial Lion to show how serious Blackest Night was going to be in terms of killing off characters, especially since Garth had been getting a very raw deal ever since Infinite Crisis and the deaths of Dolphin and Cerdian. There is Word of God from creators such as Phil Jimenez that a few higher ups at DC did not like Tempest for not being a Badass in the same regards as Hal Jordan, which has not quelled anger from the fans who are still displeased that Garth has not shown up in the Nu52.
Captain Boomerang killing women and children to feed his Zombie father, in a desperate attempt to bring him back to life.
Nekron crosses it twice: first by causing the dead to rise and attack their loved ones, and then by killing eight of the ten resurrected superheroes (including Superman and Wonder Woman) and turning them into Black Lanterns, all the while being in an And I Must Scream state forced to watch themselves attack their friends and loved ones while slowly dying.
Padding: The Parallax vs. Spectre fight: while providing an emotional callback to Rebirth, it comes off as this when both were promptly dismissed once the fight was over.
Take That, Scrappy!: Holly Granger of Hawk and Dove, who had a thoroughly dislikable personality that, somehow, changed depending on the writer, was not liked by fans. So when Hank is brought back here, he kills her in a Curb-Stomp Battle, and in Brightest Day, Hank is brought back as Hawk instead of Holly.
Osiris had it bad enough in 52. Now, not only is he the only Black Lantern to retain his humanity, but his sister and brother are dead. And everyone is afraid of him. And Sobek is murdering people just to get to him. The poor kid just can't catch a break. Although in the end, he is given a true second chance at life thanks to the White Rings. Which gets subverted in Titans when he participates in the murder of Ryan Choi and gradually becomes the killer everyone accused him of being..
Maggie Kyle is now one too, given everything which had already happened to her in the Catwoman monthly book (which was being tortured with her husband by Black Mask, having her husband die, being forced to eat her husband's eyes, and being committed). After escaping from Black Lantern!Black Mask, she has now snapped completely and gone insane.