News of Ace's death came shortly (as in within days) after Funimation released the first dub episodes of the Alabasta arc on their site. Said arc featured him as a Guest-Star Party Member for a few episodes. It makes things unsettling...
Double whammy: when Episode 437 came out. Luffy's determination to reach Ace is to the point that he gets up even though poisoned, and beats his head against the bars of a cell to break out. Even considering the expression on Luffy's face, watching that scene was hard, when you consider that all his effort and sacrifices will ultimately be in vain.
Also, remember Bon Clay's Heroic Sacrifice and his facing down Magellan while Luffy and Co. got away? Yes? Remember Bon Clay's last words to Luffy? "YOU MAKE SURE YOU SAVE YOUR BROTHER!!!" ...Ouch.
Basically, to everyone who's read through the Marineford Arc, yeah... so how's watching any of the anime episodes holding up for you?
There's a villainous example with Arlong; his rants about fishmen superiority over humans ("Heaven gave us the power to separate us from you! So WE ARE DIFFERENT! Humans are lower than fishman from the day they're born!") takes on a horrifying twist when it's revealed that fishmen have been savagely persecuted by the World Nobles and he in all likelihood was once a slave. And then think about how the World Nobles see themselves as gods; Arlong's ranting comes off as deeply embittered counterarguments against that kind of thinking instead of standard Fantastic Racism. It also turns out that Arlong's fortress, Arlong Park, was modeled after the amusement park in Sabaody Archipelago, which Arlong apparently admired. Camie visiting that park results in her getting kidnapped and nearly sold into slavery, so perhaps there are other fishmen and mermaids who wanted to go there but couldn't because of the dangers.
Arlong killing Bellemere has another Tear Jerker layer to it. His former captain, Fisher Tiger, gave his crew the command to not harm humans, no matter what. Not only did Arlong rob Nami of her mother, he also broke his promise to his captain.
In Volume 15 SBS, Oda explains sailing ceremonies, where a bottle of liquor is broken against the bow of a new ship to celebrate its completion. If the bottle doesn't break, the ship is cursed with bad luck. Right after that, Oda drew a short scene where Kaya is performing the ceremony for the Going Merry. The bottle doesn't break.
In the Jaya arc, Sanji and Zoro both bring up the possibility of getting a new ship to replace the damaged Going Merry, which Usopp yells at them for. Anybody who knows what happens to the Merry later on will find that brief moment to have a much stronger impact. This is compounded when Luffy reassures Usopp by calling Merry an irreplaceable crew member after Zoro suggests it. Makes the future event of Usopp leaving the crew, and dueling Luffy even more heartbreaking. Even worse, the snapped keel (the main reason why the Going Merry can't be repaired) was collateral damage from Bellamy beating up the Saruyama Alliance during that arc.
In the Post-Enies Lobby arc, Zeff and co. of Baratie say that they will hang up the badly-drawn poster of Sanji and say that he lived and worked there. Later on, Judge blackmails Sanji with a picture of Zeff and reveals that he knows all about the Baratie. The chefs' flaunting may have been what caused Big Mom's intel network to link Sanji and Zeff.
In the Sabaody Archipelago arc, Duval wears an iron mask to hide his face because it looks exactly like the drawing used for Sanji's wanted poster. Turns out that Sanji was forced to wear an iron mask during his childhood because his father didn't want to see his face, both figuratively and literally.
In the Punk Hazard arc, when Momonosuke first encounters Luffy, he says that Luffy can't be a pirate because pirates are giant men, weighing 400 kg, and are more fierce looking. The man who best fits that description is Kaido, who we later find out, killed both of Momonosuke's parents.
In the Thriller Bark arc, Lola kept asking men, particularly strong men, to marry them, and the caption reveals that she did this over 4,000 times. The Whole Cake Island arc reveals that by running away from an arranged marriage her mother Big Mom set up, she screwed up a very important political union that could have given her enough power to defeat her rivals and become Pirate King. In any case, Big Mom is still very sore about that, and Lola could be trying to make it up to her with her casual marriage proposals, unaware that Big Mom has disowned her and plans to kill her for her disobedience.
To add on to events related to the Clear Clear Fruit, someone else far more dangerous ended up beating Sanji to it: Shiryu of the Blackbeard Pirates, to be precise, meaning the Straw Hats are likely going to have another run in with the fruit's powers.
The Straw Hats find out in the Dressrosa arc that women in Dressrosa are notoriously "passionate" and it's a common occurence for them to stab men who cross them or just stab them in betrayal. Zoro comments that a Chivalrous Pervert type like Sanji will "get stabbed for sure" to which Sanji remarks that he wouldn't mind. It was funny at the time, but two arcs later Zoro's words echo when Sanji's chivalrous nature and soft spot for women ends up getting him metaphorically stabbed in the back by a very sadistic Bitch in Sheep's Clothing.
In the Enies Lobby arc, Kalifa would say "that's sexual harassment" when her superior, Spandam, did or said almost anything. Following the Harvey Weinstein incident in 2017 along with victims of sexual harassment coming forward with the #MeToo movement, this quirk lost its humor.
At the end of the Syrup Village arc, Luffy invites Usopp to join his crew, despite the fact that Usopp isn't particularly strong (unlike Zoro) and doesn't fill any necessary roles (unlike Nami and most of the other Straw Hats) simply saying they're friends. At the time, it seems like a nice thing to do for his new friend, but in the Water 7 arc, Usopp seems to believe Luffy brought him along out of pity despite the fact that Usopp's ambitions are nowhere near as lofty as Luffy's.
Zoro mocking Sanji's Ball on his head as a crown of "Moronica" from the Long Ring Long Land arc has became harsher after the reveal of Sanji's past as a Vinsmoke family in the Germa Kingdom.
In the localization of the manga, after Lucci tells Sanji, "From the way you open doors, you don't seem to be a very patient fellow," Sanji snarkily says, "You're right. My parents raised me wrong." His father was a horrible person who wanted Sanji to be a sociopathic Super-Soldier, so not only did Sanji's father not raise him well, but Sanji didn't turn out the way Judge had hoped.
Lola giving Nami part of her mother's Vivre card seems like a nice gesture, until it turns out that Lola's mother, Big Mom, one of the Four Emperors wants to kill her, unbeknownst to Lola. Granted, the Vivre card turns out to be a useful tool for the Straw Hats, but in hindsight, Lola comes off as rather thoughtless.
The Marineford scenes where Blackbeard gains Whitebeard's quake powers and unleashes them on Marineford, causing Tsunamis to head towards Sabaody was aired shortly before the 9.0 Quake and Tsunami disaster in Japan.
One of Brook's most awesome moments comes from him staring down Big Mom and dismissing her threats with the line "What kind of fool would have come planning to die?" Later that arc, it turns out Pedro did come planning to die, since he got most of his lifespan stolen the last time he encountered Big Mom and is determined to make his death count.
In at least one dub, upon meeting Ace for the first time in Alabasta Usopp drily remarks "The brother of a monster is still a monster." At the time, it was just in response to Luffy saying Ace was always stronger than him, even as kids. Becomes much harsher once Ace's flashbacks at Marineford] come to light: after being seriously labeled as a monster his whole life just for being born the son of Gold Roger, it's a wonder Ace kept his cool around Usopp the way he did.
When Shanks visit Whitebeard to warn him about Blackbeard, Shanks brings up the fact that Blackbeard scarred his face despite him being alert at the time. Chapter 1079 shows how this feat cannot be overstated: Shanks is perhaps the most proficient Haki user in the entire series, whose Observation Haki is beyond even Charlotte Katakuri's. Shanks is able to see an incoming attack long before his enemy even thought of attacking, and he can easily take his enemy out pre-emptively. That Blackbeard is able to scar Shanks despite all these factors means Blackbeard may be even more dangerous than what's shown so far.
In Whitebeard's first appearance, there is Rockstar, a rookie member of the Red Hair Pirates, whose bounty was nothing for the New World and he still was bragging about it. Turns out he has a reason to. Shanks has a very weak Grand Fleet for an Emperor, and he recruited them so he can genuinely protect them. Rockstar could stand out among those people. Kid came very close to exploiting that fact.
The incident involving Zoro and Bonney in chapter 499 wherein Saint Charloss forcefully takes a woman as his "wife", becomes a lot worse in retrospect when it's revealed in chapter 1098 that Bonney's own mother, Ginny, was forcefully married to a Celestial Dragon and that Bonney is, more likely than not, a Child by Rape. Even worse, during said incident, Saint Charloss orders his servant to get rid of a few of his wives. This becomes horrifying when you find out the Celestial Dragon who forcefully took Ginny as his wife got rid of her after she contracted an incurable disease. Who knows how many more "wives" the Celestial Dragons destroyed in similar ways?
During Marineford, Ivankov is outraged at Kuma attacking him and not reacting to his presence at all, especially once Doflammingo taunts him by saying Kuma is now a living weapon and forgot everything of his previous life, with Ivankov furiously retorting that "no one forgets my face, and it's not gonna start with you!" The Egghead arc would reveal that Kuma and Ivankov met when they were children slaves, and Kuma vowed that he would never forget Ivankov's face as thanks for helping free them.
Remember when Blackbeard almost took Bonney as his sex slave? It gets much, much darker when it's revealed that Bonney was actually 10 years old at the time of this encounter.
