Hammer's apparent death while trying to escape the Ellie Arroway, as well as the revelation of an apparently devastating plan by the colonial rebels
In the last battle of the first part, Loser being accidentally killed by Whiskey, Corona Squad being all but annihilated in seconds, Hammer being revealed as alive, Bubblegum leaving the ship with Toat, and the Icebreaker squad being disbanded.
In Arthur, King of Time and Space, there was a Wham Episode before the first Time Skip, with Merlin's death in the MASH and Contemporary arcs. Before the second Time Skip, there was a Wham week. Mark kills Tristram and Isolde in the baseline arc! And the space arc! And the Western arc! And then in the contemporary arc, where there hadn't been any violence previously! And then the heavily foreshadowed Karmic Death of the semi-evil False Guenevere is mirrored with the Unkarmic Death of her not-at-all-evil contemporary counterpart Fasha.
After the second Time Skip, we open with a Wham Episode, although in this case a positive one. You thought Arthur's role as CEO of Excalicorp was the equivilent of being High King? Nope, he's standing for President.
Avas Demon: The end of chapter two, wherein Ava dies.
'Bittersweet Candy Bowl': Chapter 51, where Lucy finally works up the courage to tell Mike she loves him... only for him to reject her on account of him already having a girlfriend. Possibly WORSE is Chapter 52, where Mike finally gets sick of Lucy's awful behavior towards him, leaving her nearly broken inside. Keep in mind that nearly the entire comic had been built upon Mike's friendship with Lucy, and his willingness to look past her attitude to see who she really was. Yeah. WHAM.
Castlevania RPG has had two, one played for comedy, the other for grimness.
The comedic one: Blacula escapes his prison and turns Succubus against Team Dracula, then takes over Castlevania. The comedy comes with the general shenenigans of the cast still applying in what is otherwise a kinda serious scene.
The dead-serious one; While exploring some ruins while in a parallel world, the team accidentally releases an Elder God, which is just as pleasant as it sounds. In the space of only a few comics, the God brutally murders Alec and Katrina's magic chooses the absolute worst moment to go completely haywire, causing her to accidentally kill Princess. This leads to her Cat Girl curse turning her fully cat, and Angel specifically states that there's literally nothing anyone could do for her now. And to top things off, the Elder God possesses Angel. The chapter ends with Elder God=/=Angel grimly telling Darkmoon that there's nothing he can do to stop it, that everything he and the party did was ultimately pointless and ineffectual, and then calmly obliterating him. Thankfully, Darkmoon turns out to be Not Quite Dead, and manages to save the day through Playing Chess With Death and Time Travel.
Cheap Thrills - Chapter 3: Jeordie is goes on a Mushroom Samba after taking spiked mushrooms. It looks like a round of "Jeordie's stupidity earns him another hard life lesson" and Jeordie's mom Elizabeth goes on the errand Jeordie was now incapable of, sharing a bonding moment with younger son Faris in the process. but that gets turned on its head when Elisabeth and Faris are killed when a semi drifts into their lane and hits them head-on.
College Roomies from Hell!!!: Mike (possessed by Satan) finally gives in to April's advances, then brutally rejects her afterwards. April responds to this Marsha playing "pretend I'm going to slit April's throat" by running Mike through with a large knife, killing him. Arguably marks the point where CRFH hits full-on Cerebus Syndrome territory.
Demon Candy Parallel just gave a huge one as of 15.5, where Jonathan has been possessed by Citoria, who uses the poor kid's body as his vessel to attack and apparently kill Victoria in a bid to take over the underworld.
Digger manages a fair few. The first that the Cold Servants are Hyenas came as no surprise to most as the nature of the dead god had been so heavily foreshadowed if they turned out to be anything else people would have objected. However Ed being Grim-Eye's father although foreshadowed was foreshadowed so subtly it came out of fricking no-where as far as most readers were concerned, but makes so much sense in hindsight and is such a heartbreaking revelation it jumps right off the HSQ metre.
Chapter 19 IN SPADES. King Cold transforms into his never seen third form, and a few pages later into his fourth form. U9 Videl is seen using the Kaioken. Her sword broke, setting free the U9 Old Kai. The mysterious shadow in U3 that had appeared several chapters earlier is revealed as Dr. Raichi... Only to immediately appear yet another unknown shadow in U3... And a few pages later, it's revealed that there's ''even another'' unseen new character at U3, U3 Bardock, who can even turn Super Saiyan. And, when everyone thought the chapter had long reached its top, Bardock has a vision of a Not Himself Vegetto attacking Gohan and Piccolo screaming that all universes are now in danger, which is then followed up on the next page with Buu in a much less solid state yelling out "This Masquerade ends now!", Frieza revealing that Ginyu might have an important part to play, Goku allying with a Cell Jr. and the Super Namek speaking! HOLY SHIT. The chapter title could not be so accurate.
In a much smaller degree, the U7 Special has an in-universe example, when Krillin, Bulma, and Gohan arrive on Namek... their very first encounter with a Namekian is... this.
Chapter 33. Vegetto finally squares off against XXI ... which ends in an epic anticlimax. This angers Vegetto enough that he nearly disqualifies himself. It angers Buu enough that he reveals he's been manipulating everyone the entire time and then he TRIES TO ABSORB EVERYONE IN THE STADIUM.
Dumbing of Age: Answers in Hennessey. Billie finds Ruth completely drunk and hides her from the fire department (which came due to the fire alarm that Billie pulled). Billie reveals that she got a DUI, which got her kicked off the cheer squad. Ruth knew that all along, and tells Billie that her parents were killed by a drunk driver. It's a big, sobering chapter of the consequences of the two's interactions with each other and with alcohol.
Fourinagoddamnedrow in 8-Bit Theater. The third one is, arguably, the whammiest because Fighter, for the first time in the comics 1,000+ , seven year run, has actually shown anything but admiration and love towards Black Mage; and Black Mage, for the second or third time, has shown genuine affection for White Mage.
And all three of them paling beside the revelation that Sarda is actually the Onion Kid, out for revenge against them for Black Mage mind raping him and killing his foster parents. Repeatedly.
You have to admit that the fourth one was really whammy because Black Mage actually killed Fighter. Granted, he's been threatening to do that for years, but he actually succeeded in doing it this time.
Ya, for all of a minute.
Also, the defeat of the Big Bad in Episode 1221; which was lampshaded in Episode 7; a wham with a set-up spanning the entire series.
The Electric Wonderland comic "Into Thin Aerynn" brings Trawn's Conflicting Loyalty between Aerynn and Natasha to the forefront, and also casts a dark light on the difficulty of maintaining a relationship in Cyberspace compared to when people spent their lives in the real world.
Erfworld: Depending on how far you took the "world with game-like qualities" thing, when we find out that people literally pop into existence, fully formed in cities, you might be hit as hard as Parson was.
Erfworld is liberally sprinkled with these, which makes it incredibly hard to predict where the story is going.
Everyday Heroes has this literally when Jane Mighty (in her old life as "Iron Jane") discovered the truth about her team leader, Wrecking Paul: he was a serial killer who murdered her best friend right in front of her.
Some readers of Goblins theorized that Kore was a Fallen Paladin due to his willingness to kill harmless characters in cold blood if he perceived them as evil, and because he never displayed any Paladin powers in his early appearances. So when he finally demonstrated that he is, indeed, a paladin, a lot of fan theories got jossed.
Housepets! has had five of them, each of them changing the comic forever, as more and more of the plot is revealed:
The first is very early, setting up the possibility for romance between Grape and Peanut, the two original protagonists of the comic. That entire arc sets up Peanut's "cat lover" status, as well as displaying the prejudices of the pet world.
The second is A Sinister Shadow, the first real darkness in the comic, where the status of pets as people is first seriously questioned, as well as showing the first human face in the form of Joel. While not obvious at the time, this arc kicked off the second major conflict of the comic, the status of pets in the human world.
The third became evident with this comic from Oops I Arced. A dream that had occurred earlier in the comic had Grape meeting a gryphon named Pete, and when she woke up, she had a gigantic feather from it despite it being (supposedly) a dream sequence. This was later followed up by the appearance of Tarot, who confirmed that magic existed in-universe, but the girl seemed a bit crazy. However, the existence of Pete was confirmed by the aforementioned comic from Oops I Arced, setting off another central conflict to the comic as Pete is unleashed, and then turns Joel (from the A Sinister Shadow arc) into a dog and gives him the name of King. Rather than being an odd one-off event, King becomes the third major protagonist of the comic, with many arcs following his struggle of fitting into the world of pets as an ex-human.
King's arc gained special significance a few arcs later, with dog days of summer revealing that Tarot is actually the avatar of a higher order being, a Dragon who is Pete's counterpart. She seems much more benevolent than Pete, but, along with the Great Kitsune, ultimately it is revealed that all three of the higher order beings - the gryphon, the dragon, and the kitsune - are ultimately playing games with the lives of mortals, and not only is King caught in the middle of it, but Tarot is shown to be not just a silly creature, but actually the avatar of a being of immense power. King rejects his role as a mere piece in a game run by bored demigods, and as such is set off on his own, stuck as a dog until the game is over, but given the promise of a reward at the end of the game, as all avatars receive. It is also implied that the dragon has an interest in Peanut beyond Tarot's interest, with the demigod herself wanting to be his girlfriend.
The next lies in Imaginate, Too!, when Grape reveals that she knew that Peanut had a crush on her all along, and the pair are forced to attempt to articulate what their relationship means to each of them. When Peanut eventually fesses up to the fact that he wants to be her boyfriend, Grape challenges him as to what more he could want - and declares that he is her best friend in the world, before kissing him. This adds a great deal of ambiguity to their relationship, as from there on the pair are seen snuggling periodically, calling into question both of their extant relationships as well as the exclusivity of it. While it is obvious that Grape and Peanut are taking their boyfriend and girlfriend considerably more casually than humans do, other relationships in the comic range from being of similar seriousness (Bino and Sasha) to being much more serious (Fido and Sabrina), and it is not really clear that Maxwell understands the depth of their relationship - though Tarot said from the very beginning that Grape could take him if she was willing to reject Maxwell, something she didn't want to do.
More than twenty arcs later, the Trial in Heaven reveals that not all is what it seems with the game of the gods. While Pete had been shown time and again to be a jerk, self-concerned, conceited, and ultimately appearing to care little for mortals, this is all turned on its ear as it is revealed that not only does Pete care, or at least has cared about mortals in the past, but it is revealed that the Dragon is not the kind-hearted creature that she seems - it is heavily implied that not only has she been meddling in the affairs of mortals, but in their love lives, with two of her followers dating two creatures that Pete was interested in, and the ex-boyfriend of one of said followers dating a third - all conveniently ruining Pete's own plans, but implying that all of their relationships may be, to some extent, a sham set up by the Dragon to prevent Pete from winning. Worse still, it is implied that the goal of the game that Pete and the Dragon had disagreed upon hinged upon the equivalence of humans and the other animals which inhabit the world - and Pete, not the Dragon, was on the side of the equivocation of human and animalkind, with the Dragon opposed to it. Thus, rather than the black and white conflict as it had appeared before, both sides were painted in gray - Pete is a jerk, but the comic is meant to lead the readers to sympathize with the pets, and King's arc in particular shows the difficulty of the transisition between human to animal - as well as the fundamental difference between the mindset of many animals and many humans, though the wolves had also worked to blur that line in the other direction by living as people, and far more responsible people than the ferrets, their benefactors, do. It also sets up for Pete having some sort of backup plan, but because of the Unspoken Plan Guarantee, we still don't know whether it has come to fruition.
Who can forget about Jungle Fever? This Arc focuses on Fido who finally confess his love of the cat name Sabrina in front of everyone in Babylon Gardens. Some are shocked while some already knew that.
And now, as of April 2014, King has finally figured out that Pete still has an ace up his sleeve, which in a condensed form means that Pete is not forfeiting the cosmic game he's playing. Furthermore, he doesn't actually need him to fight as his avatar. However, it doesn't stop Pete from continuing on with his contract to King, just to torture him some more. Except, in a completely unexpected twist, Bailey takes the fall for King and signs Pete's contract, becoming his avatar. Now she has been whisked away to who-knows-where to duel against Spirit Dragon, where it is expected that she will be gone for a very long time from reality's point of view.
It's Walky! (back when it was still Roomies!) had Ruth die saving a drunk Danny from getting smashed by a semi. Prior to this, the strip was pure drama-free Sitcom. The shift in tone may have been 100% intentional, since the storyline immediately following that shifted the strip fully to Its Walky.
Perhaps special note goes to strip 394 where Liquid has to murder a likable hacker attached to his team in order to keep a secret. As the author himself posted on the news page when the comic first came out "Shit just got real".
In Max Overacts, during Klaus' birthday party at the zoo Curio gets trampled on when he accidental falls in a elephant pit and after the party Max finds out the Janet got an role on a tv show and her family just let for Vancouver.
Strip 942. After countless theories and ridiculous guesses, we finally get an explanation for what Miho, one of the greatest mysteries of the comic, is. After calling Yuki a Magical Girl, Yuki angrily follows her (not really paying attention to where they're going), and demands Miho stop and explain herself.
To say nothing of the revelation that the titular filing accident is literally the only reason Emily is still alive.
Mob Ties: Once you reach Issue 7, Revelations, be ready for a Wham Episode every Issue, because once it's revealed that Mika was the victim of a violent rape so traumatic that it has left her severely traumatized to the point that she cannot remember it and passes out when anyone mentions it to her, the plot kicks into high gear.
And the Whams become even bigger when Issue 14 rolls around, and the Big Bad Bengal appears.
Romantically Apocalyptic: Pages 104 and 105 reveal that Captain doesn't actually exist. Captain is merely part of Snippy's split personality.
Roommates's Dark!Jareth arc... Who thought that that mostly harmless Trickster is capable of attempting to murder his best friend and his love interest and with forcedCharacter Rerailment make the other characters repeat the same villainous acts that destroyed them. And all because he tried to become the hero but the storydidn't let him and suffered a backlash.
Also Kings War, which revealed: who the Scribble Person is The Story, what the source of the vine border is The Shadow Child aka Disbelief and what happens when an OC dies they move out of the comic.
Scary Go Round has a Wham Episode during the second Super Crisis Quests storyline when we learn that the character previously thought have been to be the Devil was just a character actor named Old Nobby, and the Devil was revealed to actually be crazy old Ralph after Nobby's death.
Shades, Chapter 10: the bad guys get parliament suspended and put a puppet in charge of the UK.
Something Positive gave us a wham in the "Just Today" story, where Fred and Faye spend a day together, and Fred struggles on how to tell her he has Alzheimer's. He decides to wait until tomorrow, which is where the wham comes in: Faye dies in her sleep overnight.
Issue Ten of the infamous Sonichu, in which several of the main characters brutally murder a handful of people whom the author believes have wronged him in life. The childish aspect of the artwork could make it even more disturbing to some people.
Sonic The Comic Online has the Kane arc which has Sonic's fall from grace and "exile" from Mobius in which he was disgraced in the eyes of every Mobian even Amy (par Tails) after a malicious smear campaign by the Kane Broadcasting Company leading to Sonic being a fugitive and being accused of being a terrorist.
Issue 262 Has the fact that Bob Beaky is Sonic revealed to all of Mobius blowning Sonic's Bob Beaky disguise and in Silver's future Sonic has been Un-Personed and replaced in the history books by Tails.
The Super Fogeys first is when Dr. Rocket is revealed to be Herman, a shapeshifter the real Dr. Rocket used to try to ruin Captain Spectacular's reputation. Herman had reformed and was forced to become Dr. Rocket (the explanation how isn't so good), but after a blow on the head, this process broke down and more and more of Herman gradually begins to show. The reader's clue is when Dr. Rocket acquires a stutter, which Herman is shown to have in a flashback before the reveal.
This pales in comparison to the fact that the mysterious Dr. Klein and the Third Man are actually Jerry, Captain Spectacular's sidekick. The comic archives are FULL of subtle hints and clues — from the fact that Jerry is never seen in the same panel as Dr. Klein, to Klein's affection for Jerry and Spy Gal (Jerry is in love with the latter), to Jerry not having any powers yet was able to 'survive being thrown into a volcano' (the Third Man can appears to use a dimensional gate or can teleport), to similarities between designs, and the list goes on. Best of all, it is clear that this was planned from the very beginning.
Tales of the Questor: Old Secrets story arc: Quentyn's town learns to its horror that an old forgotten debt incurred by Quentyn's predecessor has grown until most of the town will be literally repossessed. Quentyn, up till now struggling as an underappreciated hero most of his town sneers at, volunteers to renew the original quest to cancel the debt and the series becomes an extended adventure of The Quest that makes him a hero of great honor in his community and beyond.
Terinu: Leeza confronts her father after discovering that Humanity knew about the Dominion using the Ferin as power sources and committed genocide against them to disable the Dominion. Then her father throws her in jail to keep her quiet.
As seen in the image at the top of the main page, VG Cats references this in a Lost Episode of Tom and Jerry, which is a deconstruction of the slapstick violence and Amusing Injuries the title duo suffer. Jerry is charged with aggravated assault, given a lengthy jail sentence, while Tom suffers irreparable brain damage and spends the rest of his life as an invalid.
YU+ME: dream does this in Issue 9, which was kinda unexpected (despite, you know, the title) due to the readers' emotional investment.
Part 2: Issue 11 reveals that Lia was once a real person. In her dreams she befriended Sadoko but in real life she fell for a man. Her boyfriend died in WW2, Sadoko impersonated her boyfriend and made her believe she was in heaven. Eventually Lia learned the truth, her consciousness was kidnapped, and she became a Eldritch Abomination. Several other chapters are this, including the final two, where we learn Sadoko was a living person and we learn who Clandy truly is.