- After fans have debated on the legal and moral implications of the illegal imprisonment of metahuman criminals in the Pipeline of S.T.A.R. Labs, it was shown in "Rogue Air" that Joe was not comfortable with the idea and in the same episode DA Cecille reacts with realistic concern and disgust at the idea. From Season 2 onwards, Iron Heights Prison has a metahuman wing and thus the majority of evil metahumans would be imprisoned there so they can have due process. Team Flash only use the prison when it is strictly necessary.
- Iris West is changed from a journalist to a criminal psychologist, likely to avoid Lois Lane comparisons. However, in the second episode, we learn she's taking a journalism class for an elective, and she's soon doing articles about the Flash, ultimately being offered a job as a reporter.
- In "Rogue Time" after learning Barry's Secret Identity, Captain Cold makes a deal with Flash. He gets to be a supervillain like he wanted, and doesn't tell Barry's secret, but he won't kill anyone anymore.
- For those who think Barry is depicted as too young compared to the comics (see Older Than They Think below), "Tricksters" reveals the in-universe justification for this, as Thawne completed the Particle Accelerator — and caused Barry to become the Flash — at least 7 years earlier (2013) than the real Wells did in his original timeline (2020).
- After Iris finally finds out the big secret, she unloads on Barry and Joe with everything the fans had been saying for months about how silly and counter-intuitive their insistence on keeping her in the dark had gotten, for which we're clearly supposed to be on her side.
- The Flash gets a white background on his logo in place of red, as many had clamored for the suit to be closer to the comics.
- Characters comment on the lax security of STAR Labs, which viewers and reviewers noticed, and Cisco claims to have made improvements to the system so nobody can just walk in. Then Hunter Zolomon does just that.
- Many complained that Cold was just too powerful in Season One, as he always managed to wriggle his way out of justice in every one of his appearances. In his first appearance in Season Two, he finally gets sent to Iron Heights and stays there a good long time until the mid-winter finale.
- Barry is now far less cavalier about his secret identity than in the first season, to the point where Caitlin almost blowing it to Lisa Snart is treated as a shocking moment.
- They seem to be using Earth-2 as a placeholder to introduce elements they couldn't squeeze into Season One, like Atlantis (although the character associated with it might still get Exiled from Continuity) and Gorilla City (an important part of the Flash mythos in general and Grodd's backstory in particular).
- A common complaint after Season One's finale is that the writers killed off Eobard Thawne without explaining the origins of his grudge against Barry. "The Reverse-Flash Returns" takes the time to do exactly that, with Thawne's motives being almost identical to his origin from the comics.
- Due to the outrage of Deadshot's death due to blatant Executive Meddling during Arrow Season 3, an Earth-2 version of him shows up.
- Barry has caught a lot of flak from fans for claiming to be "the fastest man alive" while every enemy speedster introduced so far has been much faster than he. It was later revealed that Zoom, like Trajectory, is using the deadly V9 drug to increase his speed, while Reverse-Flash fueled his powers with a tachyon device, meaning that Barry may well be faster than they without their enhancements.
- In Season One, Hartley got a lot of hate for being a far cry from the Hartley people wanted to see: namely one who was a good guy or at least Affably Evil and a friend of the Flash. Well, "Flash Back" is basically one long apology for that and retcons Hartley's current personality into what fans wanted, so he's now a stable guy who helps the Flash and is far less of an asshole even in the "original" story.
- Similar to Deadshot above, an Earth-2 version of Laurel Lance appears only a few weeks after the Earth-1 character was killed off on Arrow to massive backlash. For added measure, while Laurel's counterpart is a criminal and goes by the alias Black Siren, she is a metahuman and her outfit downplays Black Canary's Adaptational Modesty in Arrow.
- The character initially presented as Jay Garrick not only was much younger than his comics counterpart, but also has a very different costume (the bright yellow ligthning symbol was reduced to a barely visible outline). And he was reveled to be the season's villain Zoom. By the season's finale, however,it turns out that his real name is Hunter Zolomon (the identity of the second Zoom in comics), while the real Jay Garrick is a hero, whose age and costume are much closer to the comics version. Being played by John Wesley-Shipp also helped.
- Wally becoming Kid Flash in the premiere, since he went all through Season Two without getting powers. While this only occurred because of the Cosmic Retcon at the end of the previous season, Wally eventually gains his powers "for real" in the post-Flashpoint timeline as well.
- Doctor Alchemy, Mirror Master, and the Top, high-profile Flash Rogues in the comics, are confirmed to be joining the show, after Season Two didn't introduce any new members from the comics' Rogues Gallery apart from Zoom (who operated independently from the Rogues in the comics).
- The revelation in "Killer Frost" that Savitar may be responsible for the changes to the timeline and not Barry since many viewers thought that Barry was being punished way too harshly for wanting to save his mom.
- For those who fall in the "cut Barry some slack for Flashpoint" camp, the fact that both Oliver and Kara show unwavering trust in Barry during "Invasion!" despite learning of his hand in changing history was a welcome sigh of relief following an entire season's worth of people pouring their grievances upon Barry's head. Oliver goes the extra mile by a) telling everyone to save the drama until after the Dominators are dealt with, b) confiding in Barry about how helpless he was to save his parents, and c) assuring Barry that anyone else—himself included—would've done what Barry did if they were presented with a chance to save their family, all in all trying to get Barry to realize that, contrary to popular belief, he's not entirely to blame and should stop agonizing so heavily over what happened.
- Supergirl being the only one of the brainwashed superheroes to be presented as a possible threat to Barry in the second part of the "Invasion!" crossover after many believed he jobbed to Arrow and Vandal Savage in the previous crossovers.
- Several fans have complained about too much of Iris' character is being strong for everyone else and rarely talking about her feelings, despite the numerous upheavals she's been through (boyfriend who killed himself, back from the dead mother, long-lost brother, aforementioned mother dying). This is especially because of the potential Unfortunate Implications of the only black woman on the show not getting to express her emotions, instead swallowing pain to help everyone else. These fans are gratified that she seems to be expressing some emotion and vulnerability regarding her possible death at the hands of Savitar.
- It's frequently complained that when a new speedster comes that's faster than Barry, the focus is for him to get faster than before. With Savitar, no mention of trying to get Barry faster, only prevent the events of Iris dying by Savitar. With Reverse-Flash and Zoom, there was at least a gap that Barry could reach and could keep up with them for a time. Savitar's speed was enough that Barry's speed was in slow-motion by comparison. It's a welcome change to see the team deal with an evil speedster in a different way.
- Cisco's falling out with Barry as well as the disdain he held for him was thankfully put to rest in "Invasion!". Now in the second half of the season, especially in "The Once and Future Flash" the writers have followed this up by making the effort to include scenes of Cisco and Barry happily hanging out and Cisco reaffirming that Barry is his best friend.
- Towards the end of the season it seemed the shows writers were also acknowledging fan complaints by slowly reintroducing the show's original lighter tone by averting Iris' death and having Barry reach out to Savitar and offer him redemption (albeit unsuccessfully) before finally displaying Character Development as a more mature hero by owning up to Flashpoint and taking Jay's place in Savitar's prison within the Speed Force.
- Barry finally getting a new costume, on two counts - 1) it swaps out the darker red & actually puts the Scarlet Speedster in scarlet, and 2) it brings the Flash costume up to the same standard as the other Arrowverse costumes, which had been increasingly outclassing the original suit.
- The showrunners were very aware of how sick fans had gotten of the repetitive season arcs of the first three seasons, and were quick to assure us Season 4's Big Bad would not be another speedster. He's also revealed in full right in the season premiere rather than the increasingly ridiculous attempts to build a mystery around their identities. Furthermore, the end of the sixth episode has Team Flash pinpoint his location and prepare to apprehend him, with Barry actually noting they have an opportunity to get a drop on the bad guy for a change.
- There had been complaints from fans that Barry wasn't as fast as he ought to be, given that not one, not two, but three evil speedsters were shown to be faster than "The Fastest Man Alive" and that he struggled against villains who, by all rights, should have been severely outclassed against him. "The Flash Reborn" rectifies this, making it abundantly clear that post-Speed Force Barry is faster than any speedster has ever been (counting Wally) and showing him defeating the Samuroid with minimal effort.
- After many complaints about the Darker and Edgier take of Seasons 2 and 3, the series has become more comical as an attempt to be more like Season 1. During SDCC, producer Todd Helbing directly stated in a very rare admission of guilt on the part of a creative team that they realized how dark the Savitar plotline had become and that Season 4 would be much funnier in comparison.
- However, this direction has led to criticism that the show is now ''too'' goofy for relying too much on jokes to lighten the tone rather than balancing between humor and heart as seen in earlier seasons.
- Season 1 and 2 would provide lovely scientific Hand Wave explanations for the various metas, while Season 3 tended to plonk them in with no justification behind their powers, aside from Mirror Master. Season 4 has gone back to its roots and has Wells or Cisco unloading the science, and either they, or Barry, Iris or Caitlin putting it into more general and understandable terms.
- After The CW has overused the Relationship Revolving Door to the point that the couple loses popularity, the creators have outright assured the audience that Barry and Iris' wedding will indeed be happening as a part of the epic crossover event Crisis on Earth-X, after events from Season 3 threatened to have them follow suit.
- After Caitlin's situation with Ronnie and Hunter, Caitlin will not be, aside from slight flirting here and there, thrown into yet another doomed love story. Both the creative team and Danielle confirmed this, firm in their belief that Caitlin needs to focus on herself before even considering getting back into the dating scene.
- Regarding the overwhelming fan outcry over Barry and Iris' wedding being spoiled by Felicity's last-minute hijacking so that she could abruptly get married to Oliver (and the crossover as a whole doing nothing to reverse the general fandom sentiment that Olicity is a major Romantic Plot Tumor), the following episode shows that Iris and Barry weren't happy with that and just tolerated them to avoid making a scene after all the crisis on Earth-X, so they send the Queens' gift to the "return" pile. It seems the writers weren't particularly happy about that either.
- Killer Frost developing into an Anti-Hero as many fans were annoyed how last season she was evil for no other reasons other than her powers made her so. However, this was criticized because it left Caitlin underdeveloped.
- Season 3's take on Flashpoint was strongly criticized for being solved in just one episode, and a similar phenomenon occurred with the Season 3 finale and Season 4 premiere. In "The Trial of the Flash" arc, it's made clear Barry's imprisonment would last longer than a single episode.
- Season 3 was criticized for not giving enough pathos or characterization to the Big Bad Savitar until very late in the season, making it difficult for the audience to really care about him and what he does or will do. note By contrast, Season 4's Big Bad crosses the line hard in the midseason finale, the devastating effects of which we see in the following episode, leaving the audience excited for his inevitable downfall. Also DeVoe's plans are a higher menace than Savitar's, which were seen as insufficient to sustain a big bad.
- Since Barry's acquittal and "DeVoe"'s appearance were way too suspicious, said acquittal not being the legal exit Barry was insistent about and the "Trial of the Flash" plot was unbelievable on the whole, it is revealed not everyone believes his innocence and David Singh has to suspend Barry indefinitely until his innocence is unambiguously proven.
- The ending of "Run, Iris, Run" has Iris decide to resume her blog, after many complaints that people didn't know whether she was still a journalist or not and that her journalism was forgotten in favor of Team Flash. It finally explained unambiguously that Iris left journalism. In "Harry and the Harrisons" she uses her journalistic skills to research about DeVoe and publish an exposé against him.
- Some complaints about the Monster of the Week format are that they barely had anything to do with the Myth Arc of the corresponding season. The batch of metas this time around figure heavily into the Thinker's plot, which also gives Team Flash a legitimate reason to Gotta Catch Them All.
- Despite the praise some fans gave to the actors who portrayed DeVoe after he began taking over different bodies, others were disappointed that Neil Sandilands stopped playing the character so soon. After he stole Ralph's body in "Lose Yourself", DeVoe used his powers to get his old appearance back.
- The Flashs costume is changed once more, this time ditching the previous season leather suit, which could occasionally look too big on Gustin, for a more comic accurate spandex.
- To compensate for the underutilization of characters by limiting them to S.T.A.R. Labs, Todd Helbing said Season 5 would explore more of Iris' journalism and Ralph's detective skills.
- In the second episode, Iris is shown investigating on her own about the death circumstances of one of Cicada's victims. This is a response to the complaints that Iris' journalism was overlooked and that Iris' role was poorly executed in Seasons 3 and 4.
- After fan dissatisfaction with the handling of Ralph last season given his Adaptational Comic Relief causing his skilled detective side to be hit with Badass Decay, this season has Ralph being a far more competent detective. He also became a Nice Guy and a braver hero.
- Todd Helbing said he learned on "The Trial of the Flash" that the series need more arcs. The audience has criticized how Seasons 3 and 4 overused filler and Idiot Plots to pad out the 23 episode quota.
- Crisis Crossover "Invasion!" had the problem that the part of Arrow coincided with the Milestone Celebration of the 100th episode, and as a result the episode was disconnected from the crossover itself, not that it was any less awesome. To avoid this in Elseworlds (2018), the crossover episodes will be the ninth ones of each season.
- In the second episode, Barry seems to have finally learned that Team Flash keeping secrets from each other has never ended well, and that episode opens with him and Nora telling the others the truth about why the latter is here.
- The show finally addresses how Caitlin's meta powers bear no resemblance to the way they work for everyone else in the Arrowverse in creating an entire separate personality, revealing that she came by them in a completely different way.
- After fan dissatisfaction with Godspeed being reduced to Nora's Starter Villain, Godspeed was brought back in Season Six for a much larger role, as well as being far more competent and thus has evaded capture so far.
- The Season Five costume got a lot of flack for removing the chinstrap & gold lining from the previous costumes, which had the effect of making the headpiece look out of place & the costume as a whole just being too much unbroken red. The Season Six costume brings the chinstrap & gold lining back, and finally switched the ear pieces from lightning bolts to the Mercury-inspired wings - making the suit just a set of gold boots away from being an exact recreation of the comic book suit.
- Some fans were dissatisfied that Iris' journalism was brought back in season 5 only to be ignored in the second half of the season, so the announcement in interviews that she'll have a journalism-centred arc for all of season 6 and will even have employees excited many.
- Season 5 had a polarizing Arc Fatigue regarding Orlin Dwyer's Cicada being the main Big Bad for 16 episodes straight. Season 6 will instead have two major villains, each for the first and second half. Ramsey Rosso / Bloodwork, will be the main villain of the first half.