Arguably it's Jason who receives the beating here at the hands of the Flamingo, a killer in a bright pink costume that would have killed Jason and his sidekick Scarlet if Damian and Dick had not come to his rescue. It was also Flamingo who shot Damian in the back, paralyzing him.
Jason's stint as Robin ended way back when in the 80's in A Death in the Family, where he himself got served an astoundingly brutal for the time No-Holds-Barred Beatdown courtesy of The Joker and a crowbar, who then blew up the warehouse where it took place. DC at the time ran a poll asking the readers if Jason should survive or not; turns out the votes in favor of killing him off outnumbered those in favor of letting him live, so this was in effect DC itself allowing its readership to do this themselves. It's also significant that hatred for the character was so great even afterwards that it took almost 25 years for it to abate enough to bring him Back from the Dead (and it's far from totally gone, too).
Damian was originally intended to die in the very same arc he debuted in, but by his death being aborted, went on to do increasingly amoral actions no Bat-Family member could normally get away with. Even when his death finally happened at the hands of Heretic, his clone created by his mother Talia al Ghul, nobody really condoned him for his earlier actions and he was eventually resurrected. But after long periods of continuing to remain amoral, and Aesop Amnesia being used to snuff out the few moments he did show decency, the Teen Titans proved to be far less patient with him than Batman ever was. The team was angry at him for locking supervillains such as Deathstroke, Brother Blood, and Black Mask in their base without telling them, torturing them severely, and if him losing his new love interest Djinn to Crush wasn't enough, Batman would ultimately agree with the Teen Titans and help them hunt him down enough that Damian decided to abandon the Robin name entirely.
Blackest Night: Terry Long, one of the less popular elements of Marv Wolfman's run on the Teen Titans, is brought back as a Black Lantern and ends up being killed by Donna Troy herself, with a comment about moving on that has some interesting Applicability.
In DC Rebirth #1, Pandora, the character who was thought to be responsible for the divisive New 52Continuity Reboot (and who is thus heavily associated with the reboot by fans), is casually murdered by Doctor Manhattan.
Both core Superman books in the DC Rebirth line took jabs at the New 52 Superman (NuSupes). The guy was not well-liked due to being angrier, more prone to violence, having an unnecessary power and having a relationship with Wonder Woman, and was killed off just prior to the relaunch to make way for the pre-New 52 Superman (Superdad). Examples include:
Action Comics' first arc having Wonder Woman tell Lois Lane that her love for Superman feels more "true". Wonder Woman had previously been in a relationship with the New 52 Superman that wasn't very well received, so this is basically Diana saying it wasn't true love.
The Take That! towards the Superman/Wonder Woman relationship even occured in Wonder Woman (Rebirth), Diana's own series. There she tells Steve Trevor, her most frequent love interest who got sidelined to make way for NuSupes, that she was with NuSupes because it was "easy". Basically Greg Rucka was jabbing at the decision to pair the two up through Wonder Woman.
Superman (Rebirth) has Lois say that, when it comes to Superman, "there's nobody better" when referring to Superdad.
Superman Reborn has a subtle but still noticeable example if you're up on your Superman lore. The story reveals that Superdad and NuSupes are actually two halves of the original Superman. Specifically, that Superdad is the blue energy of Superman, while NuSupes is the red. This is actually a new version of the Superman Blue/Superman Red storyline from the 90s, wherein Superman was two energy beings that were, well, blue and red. In that story, it's eventually revealed that the blue Superman is the real one. Yep, the writers were sneaky with it, but they got in one last jab at NuSupes before he was written out of history altogether — Superdad, despite being one half of the "true" Superman, is still the "real" Superman. When the two fuse back together into the "true" Superman, said Superman is basically entirely Superdad anyway, since he's got Superdad's history, family and personality, so there's another Take That!.
The Flash: In The Flash: Rebirth, while he isn't hated in-and-of himself, the run did see Barry finally get called out on the more selfish actions he took since his return, having him finally deal with the fallout of destroying his relationship with Iris and Wally's life, trying to keep Iris in the dark with "Sins of the Father" finally allowing her to learn the truth, "The Perfect Storm" deconstructing Barry's post-resurrection Protagonist-Centred Morality and the focus sorely on him at the expense of others, "The Flash Age" seeing Paradox outright say Barry was only remembered due to his death and he should've stayed dead. Granted, fans of Barry themselves, find this controversial, but fans of other characters who've gotten annoyed with how DC pushed him, they do enjoy seeing Barry finally being put to task for his actions of late. That said, others argue that the use of this trope rang hollow due to the fact that Barry never actually makes a genuine effort to fix his mistakes other than standing around and looking sorry. It comes across more like Williamson is paying lip service to the fans who wanted Barry to answer for the awful things he's done without actually punishing him for them.
The vocal dislike of Brian Bendis's update of the Legion of Super-Heroes (2020) gets acknowledged in Green Arrow (2023) when Lian Harper and Connor Hawke find themselves stranded in this version of the 31st Century. Lian grows annoyed with the Legion's refusal to look for her grandfather Green Arrow or answer any of her questions, to the point of bluntly asking if the Legion does anything. Keeping in mind the chief complaints about Bendis's Legionnaires were how they spent all their time rambling about nothing and not actually doing anything, Lian's complaints mirror those of the readers.
Lian Harper: Are you sure you're the Legion of Super-Heroes and not the Legion of people who fly around and do nothing?
One of the (many) controversial decisions made during the New 52 was Lobo being reintroduced as a slender, clean-shaven Pretty Boy instead of the grungy, musclebound slob fans had come to know and love. DC Rebirth later brought back the classic Lobo and Hal Jordan and the Green Lantern Corps had Brainiac shrink down the new Lobo and trap him inside a containment jar, which the Green Lantern Corps then refused to open.
Hal Jordan: Not that one. Trust me, better to leave him on the shelf.
Out of every death shown or implied in Heroes in Crisis, there is only one dead character no fan has gotten upset or outraged about and that's Mark Richards, the current version of the Green Lantern villain Tattooed Man. Created by Geoff Johns, Mark is largely known for his flat personality and inconsistent motivations with the only memorable thing he's done was participating in the brutal slaughter of Ryan Choi when he was with Deathstroke's faux Titans team. It's telling more people were upset about Gunfire of the New Bloods dying as well as the incredibly minor Titan the Protector getting killed off than Tattooed Man.
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.
Almost all the titles introduced in the Bloodlines crossover flopped after less than a year, with the lead characters being relegated to Comic-Book Limbo. This was brought up in-universe in JLA/Hitman, where Green Lantern and The Flash mockingly claimed that the Bloodline heroes were a bunch of incompetent losers that everyone else in the superhero community looked down upon (this had extra self-congratulatory subtext from Garth Ennis, since Hitman had been the one character with a Bloodlines-related origin to actually take off).
Earlier, Ennis had gotten in a similar jab by introducing the DC One Million version of the Bloodlines hero Gunfire, only to have the character accidentally kill himself in an utterly humiliating manner.
Years later, the mainline Gunfire got dispatched by Prometheus almost comically easily, and had his hands cut off for good measure. The same fight saw his fellow Bloodpack member Anima accidentally get cut in half while trying to pursue Prometheus through a portal. Prometheus then proceeded to chuck her lifeless torso into the Void Between the Worlds outside his lair, which he explicitly likened to putting the trash out on the curb. Ouch. Ironically, this was in an issue that was dedicated to putting Prometheus through his own Rescued from the Scrappy Heap arc.
And a number of them (specifically Mongrel, Geist, Ballistic, Nightblade and Razorsharp) were killed off by a casual glance (a heat vision glance, that is) from Superboy-Prime during Infinite Crisis.
Secret Six has Tarantula's death. The character is not popular due to the epic Double Standard involving her actual raping of DC Comics fan favorite Nightwing, and the fact that she was accepted onto his team, the Batfamily, afterwards. Suffice to say, many cheers were had when she finally got her comeuppance and died, being hit by an onslaught of super powers, which promptly destroyed her body and sent what's left of it off a bridge, into a river.
Wonder Woman: The Hiketeia: The version of Batman in this story has all the worst elements of the self entitled "BatGod" that he kept cycling back into under different writers, who was cruel and dismissive of his allies for no discernibly reasonable reason and treated as always right. As this characterization of Bats had long since become a fan pet peeve seeing him get taken down a notch was cathartic for a significant percentage of readers.
