The Flash introduced several speedsters from the DC Universe into the Arrowverse, and each of them was changed in the process. Ever since it began in 2014, the Arrowverse series hasn't been shy about using as many heroes and villains from Flash's mythology as possible. While Barry Allen is the central figure of The Flash, there are multiple key characters associated with the hero in DC Comics. Throughout the decades, the Flash Family has become one of DC's most beloved legacies, and there have been several heroes that have either carried the mantle of The Flash or become their own speeding hero.
But just like there have been many who have worn the mantle of The Flash, there have also been lots of villainous speedsters to take on the heroes. Over the course of 7 seasons, the Arrowverse has brought in pretty much all of the big heroes and villains that are part of The Flash comics. While some have been on the series longer than others, pretty much the majority of them have been altered for their TV portrayal.
It's normal for creators to change various aspects of comic book characters whenever they get adapted from page to screen. Whether it's the costumes, their powers, or their family linage, The Flash has taken a few departures from the comics in order to do their own spin on the speedsters. With Bart Allen set to arrive in The Flash season 7, Impulse will be the latest DC character that the Arrowverse is changing from the comics, just like they have with their past heroic and villainous speedsters.
Barry Allen (The Flash)
Since he got introduced in Arrow season 2, The Flash's Barry Allen has been the primary speedster in the Arrowverse for almost a decade. For the most part, The CW iteration of Grant Gustin's character has followed the comics in terms of his powers, his role as a speedster, and how he lost his mother Nora Allen as a child. However, a big change to Barry's upbringing was what happened to him after Nora was murdered. While Henry was still framed for his wife's murder, The Flash established that Barry had a bigger history with Iris West as early as when they were growing up. Joe West took Barry in as a legal guardian so he didn't have to be sent to a foster home. Another departure from the comics, despite the TV show having teased it since the pilot, is that Earth-1's Barry never died or vanished in Crisis on Infinite Earths.
Wally West (Kid Flash)
For Wally West's live-action debut, Keiynan Lonsdale was cast as the Arrowverse's Kid Flash for The Flash. However, Kid Flash was reimagined quite a bit as well as he's a combination of the Wally pre-Flashpoint and The New 52's Wallace. While Wally's traditionally the nephew of Iris West, the Arrowverse reimagined him as being her brother instead as well as the son that Joe didn't know he had. After Iris's mother, Francine left her family during a troublesome time in her life, she never revealed to Joe that she was pregnant. Instead, Francine raised Wally on her own until her return to Central City over a decade later when she was dying from MacGregor's Syndrome. The way Kid Flash gets his powers is also a bit different as Wally gets his speed through the Philosopher's Stone that restored his powers from the Flashpoint timeline where he was struck by lightning.
Jay Garrick
While The Flash may be the Scarlet Speedster in modern times, Jay Garrick is recognized as the Golden Age Flash and as part of the Justice Society of America. In the Arrowverse, John Wesley Shipp didn't just play Henry Allen, but also Jay with a big twist. Unlike the comics, this incarnation is Henry's doppelganger which was revealed in The Flash season 2 almost right after Barry's father died. Jay's Earth designation was also changed for the Arrowverse as he's neither from Earth-1 as a former Flash or from Earth-2. Instead, The Flash revealed that he actually comes from Earth-3 which is normally the home of the Crime Syndicate. However, following Crisis on Infinite Earths, that's changing as Stargirl season 2 will retroactively redo his origin so that Jay's from Earth-2 where he was part of the original Justice Society.
Jesse Wells (Jesse Quick)
In The Flash season 2, the Arrowverse brought in one of the female speedsters from the DC Universe by adding Jesse Quick, who was played by Violett Beane. However, the Arrowverse reimagined her to be from Earth-2 while also changing her family linage. Her father is the Earth-2 version of Harrison "Harry" Wells, and her mother is unknown; however, in the comics, her parents are Johnathan Chambers a.k.a Johnny Quick and Libby Lawrence a.k.a. Liberty Belle. The Arrowverse version of Jesse gets her powers differently too, since she isn't a daughter of a speedster: she's hit by dark matter while helping Barry.
Nora West-Allen (XS)
The Flash hasn't only introduced speedsters from other Earths, but also future timelines — and that's where Iris and Barry's kids come in. Season 4 revealed Jessica Parker Kennedy to be Nora West-Allen, the future daughter of Iris and Barry. In the comics, they have twins named Don and Dawn Allen a.k.a. the Tornado Twins, and the Arrowverse's Nora is a reimagined version of the daughter while also being loosely based on XS. When they met Reverse-Flash during the 100th episode, he initially thought that her name was Dawn, confirming that she was named differently in another timeline. Pre-Crisis, the Arrowverse depicts Nora as living in 2049 where she had only recently discovered that she had inherited Flash's speed. But due to the time travel consequences by the end of The Flash season 5, Nora was erased from existence, while the following season has alluded to XS still living in a future timeline.
Bart Allen (Impulse)
XS isn't the only changed future kid that the Arrowverse has retooled for The Flash: Jordan Fisher was cast as Bart Allen a.k.a. Impulse who will make his first appearance in the 150th episode that will be the 17th episode of The Flash season 7. The role will be a recurring guest gig, but it's unclear how many episodes Fisher will be in. However, when Impulse arrives, his family history will be getting a big change. While most Flash fans know Bart to be Iris and Barry's grandson from the future, the Arrowverse will instead portray him as their son. Impulse still comes from the future, although it's unknown if he comes from the 31st century like in the comics, or sometime during the 21st century.
Eobard Thawne (Reverse-Flash)
Wherever Barry goes, the Reverse-Flash isn't far away — and the Arrowverse is no exception. Eobard Thawne was the first big bad in The Flash. While Matt Letscher's Eobard is still the man that murdered Barry's mom, thus setting him on a path to one day become the Scarlet Speedster, The CW changed his history: The creators still kept Eobard being obsessed with Barry and coming from the future, but after Reverse-Flash killed Nora in the Arrowverse, was stuck in the 21st century.
Hunter Zolomon (Zoom)
In The Flash comics, Eobard wasn't the only Reverse-Flash since he originally went by the name Professor Zoom. Even though Eobard is now the primary Reverse-Flash in the comics, Hunter Zolomon has also carried that title, but that wasn't the case when he joined the Arrowverse. The CW iteration portrays Hunter as a villain from Earth-2 with Teddy Sears's character first pretending to be Jay Garrick while holding the real one prisoner. During The Flash season 2, Hunter is eventually revealed to be Zoom whose backstory is darker in comparison to the comics. Arrowverse's Hunter was a serial killer on Earth-2 where he got his speed from being struck by lightning right as he was about to be executed. Hunter's reason for having to steal other speedsters' Speed Force powers is because he's dying after having experimented on himself with Velocity serums. In the comics, Hunter's actually Wally's archenemy, and while he sports a Reverse-Flash costume in his original version, the Arrowverse has their Zolomon dressed in a black suit with a demon-like cowl.
Eliza Harmon (Trajectory)
Most speedsters that have appeared on The Flash have usually been around for more than one episode either by being main characters or recurring players. But one character that only got a single episode was Eliza Harmon a.k.a. Trajectory, one of the lesser-known speedsters in the comics. In The Flash season 2, episode 16 "Trajectory", Allison Paige plays a new take on Eliza that is introduced as a scientist at Mercury Labs that Caitlin Snow befriended. The Arrowverse portrays Trajectory as a split-personality of Eliza due to getting addicted to Velocity 9. Eliza/Trajectory eventually dies as her Velocity addiction causes her lightning to turn blue as she disappears into thin air. In the comics, Eliza is actually a hero who was a big fan of The Flash, and she got her speed from Lex Luthor's Everyman Project. Similar to the Arrowverse's Trajectory, Eliza got her speed from a drug, Sharp, but ends up dying in a battle against Blockbuster when Lex strips her powers away.
Black Flash
In the DC mythology, speedsters actually have their own embodiment of death in the form of Black Flash. It always shows up when a speedster is about to die so they can take the fallen individual to the Speed Force. While the Black Flash is introduced on The Flash, the Arrowverse gives it a specific origin story and an identity. At the end of The Flash season 2, Zoom is defeated and the Time Wraiths shows up to punish him due to his actions. But instead of killing him, Hunter is transformed into the Black Flash, thus becoming the Speed Force's Grim Reaper. Black Flash is one of the foes in Legends of Tomorrow season 2 as he tries to come after Reverse-Flash because of Flashpoint. The Flash season 3 finale was Black Flash's final appearance after Killer Frost managed to kill him.
Edward Clariss (The Rival)
The Flash actually managed to introduce a speedster villain that actually belonged to Jay Garrick, even though Shipp's character never got to fight him. In season 3 when the Arrowverse adapted Flashpoint, Edward Clariss a.k.a. The Rival was introduced with Todd Lassance playing him. But the character is The Rival in name only since he has no connection to Jay and is instead an evil speedster to Kid Flash in the Flashpoint reality. Not only is his entire history different in the Arrowverse, but The Rival's costume is completely changed too and resembles the Black Racer's uniform. In the comics, Edward is dressed in a darker version of Jay's iconic outfit. After Barry resets the timeline, Edward ends up getting his Flashpoint memories and powers back thanks to Doctor Alchemy — but Rival gets defeated again and is killed by Savitar inside his cell at Iron Heights.
Savitar
The Flash season 3 introduced Savitar, who is a minor villain in the comics but became the big bad for that year. In the comics, Savitar was a short-lived Flash villain who was a former pilot; after he was struck by lightning while test-flying a supersonic jet, the pilot developed super-speed, and ended up calling himself Savitar after Savitr, the Hindu god of motion. The Arrowverse's take is completely different as this Savitar is actually a time remnant of Barry that went insane. When Flash fought Savitar originally, he created time remnants of himself and while the villain killed all of them, one survived that would eventually become Savitar. While Barry manages to stop his twisted time remnant, this Savitar was more inspired by the Future Flash in The New 52 while drawing little inspiration from the actual Savitar in the comics.
August Heart (Godspeed)
The Flash has also relied on using characters that were created recently in comics as the Arrowverse did introduce Godspeed. In the fifth season, they introduce the actual Godspeed as part of Nora's future timeline with August Heart, played by Kindall Charters. However, instead of being depicted as Barry's best friend and CCPD colleague like in the comics, August was obsessed with becoming a speedster and was experimenting with tachyons on himself. Before becoming Godspeed, August had even experimented on 17 elderly patients. After he becomes Godspeed while Nora discovers that she's a speedster too, he becomes her first villain in the year 2049.
While Nora eventually stopped August, Godspeed continued to be a presence in the Arrowverse during The Flash season 6. Team Flash faced Godspeed imposters that were all incapable of speech. A fifth one appears towards the end of that season as Barry was almost out of speed due to the death of the Speed Force. While they do defeat him, this was another fake Godspeed, but he could actually talk briefly as Barry reveals that this one was sent by someone who wants "infinite velocity." It has been confirmed that the real Godspeed will be making their debut in The Flash season 7, alluding to it not being August as they're keeping the identity under wrap. That means that whoever ends up being the actual Godspeed will in the end have been changed too in the Arrowverse.
At this point, there aren't actually a lot of other speedsters left for The Flash to use in the Arrowverse. They have pretty much used most of the big heroes that exist in the Flash Family as well as their enemies. The only ones that remain in terms of evil speedsters would be Johnny Quick (not to be confused with the heroic version), Red Death, and Cobalt Blue. But it would likely get repetitive if The Flash reverts back to just using villainous speedsters as they did in the first three seasons. But nevertheless, it's impressive how many speedsters The Flash has managed to introduce into the Arrowverse and the intriguing ways they were changed.