The Rival first appeared in Flash Comics #104 (February 1949). He is Dr. Edward Clariss, a professor at the university attended by the Golden Age Flash, Jay Garrick. He believes he has recreated the formula that gave Garrick his speed, which he calls "Velocity 9." He had heard Joan one night talking about how the Flash gave his speed to another student, which helped him get the last formula. He was bitter at the scientific community's rejection of his claims. Although he had become famous for other inventions in Europe, Clariss becomes a criminal. He wore a darker version of Flash's outfit and gave it to several other criminals. The Rival's version of the formula, however, proves to be temporary, and he is defeated and jailed.
In JSA #16 (November 2000) the Rival battles the Flash several months after his first appearance; in doing so he reaches lightspeed and vanishes into the Speed Force. Following the reformation of the Justice Society of America 50 years later, Johnny Sorrow retrieves him from the Speed Force, the Valhalla of fallen speedsters, good or evil, as well as their source of power. Sorrow invites him to join the new Injustice Society. The Rival, driven to insanity by his time in the Speed Force, races across the country on a super-speed killing spree. The Flash realizes that the Rival's path across the country spells out Clariss' name, and that the final murder will be Jay's wife Joan. The Flash is unable to prevent the Rival from killing a young boy, but absorbs his speed before he can kill Joan.
The Rival returns in Impulse #88 (September 2002), posing as Joan Garrick's doctor. Now pure speed energy, he possesses Garrick's fellow Golden Age speedster Max Mercury. After battling Jay and Impulse, the Rival escapes, still in possession of Mercury's body.
Another Golden Age Reverse Flash is a robot who wears a reversed-color version of Garrick's costume. The robot's only appearance was in one panel in The Flash vol. 2, #134 (February 1998), in which he is easily defeated by Garrick.
Eobard Thawne aka Professor Zoom, first appeared in The Flash #139 (September 1963). Originally, he is a criminal from the 25th century who found a time capsule containing the Silver Age Flash's costume. He is able to use a machine to amplify the suit's speed energy, providing the abilities of the Flash as long as he wears it. In the process, the colors of the costume reverse, with the suit becoming yellow, the boots and lightning bolt highlights turning red, and the chest symbol's white circle becoming black. He uses his speed to commit crimes. Flash had travelled to the future as he discovered an atomic clock in the capsule would become an atomic bomb due to the process. He defeated Reverse-Flash by making his friction-protection aura burn away and stopped the bomb from exploding. Despite destroying the costume, Zoom is still able to cause trouble for him. His knowledge of Allen’s dual identity enables him to strike at Allen by killing his wife Iris. He vibrates his hand through her skull after she refuses to marry him. Later he attempts to kill his fiancée Fiona. While saving Fiona’s life, the Flash breaks Zoom’s neck, killing him.
DC later revamped its continuity following the 1985 series Crisis on Infinite Earths. Professor Zoom was one of many character to undergo renovation. As seen in "The Return of Barry Allen" storyline in The Flash (vol. 2) #74-79, Thawne started out as a fan of the Flash. He gained super-speed by replicating the electrochemical bath that gave Barry Allen his powers and undertook surgery to make himself look like Allen. He traveled back in time using the Cosmic Treadmill to meet his hero. However, Thawne becomes mentally unstable upon discovering he is destined to become a villain. Though the true name of the Flash's greatest foe was not known in his time, it was known here. Zoom's mind—already disoriented by the stress of time travel as the Treadmill —had changed over the years. He arrives years after he had intended, while seeking escape by convincing himself that he is Barry Allen. However, his true, more violent nature is eventually revealed. "Barry" attacks Central City in 'revenge' for 'forgetting him', before he is defeated by Wally West, who tricks Zoom into returning to his proper time. Even though Thawne retained no memories of his journey, he felt "betrayed" by Barry and deeply hated him. Thawne began traveling back in time to seek revenge on the Flash, using his knowledge of "history" to his advantage.
Professor Zoom returns as the main villain in the mini-series Flash: Rebirth. Zoom claims to have a resurrection coming up soon, referencing the Blackest Night. In this appearance, Zoom claims to have not only traveled back in time, but also to have engineered Barry's return from Speed Force. Zoom once tried to stop Barry from originally becoming the Flash, hoping to get struck by the lightning. However, he nearly phases out of existence, causing the lightning to pass through him and transform Barry. He interprets this to imply that Barry needed to become the Flash for him to become the Reverse-Flash. He erased Barry's best friend from existence, and frames his father for murdering his mother. He is behind the reality changing event Flashpoint, and mocks Barry, who remembers how things should be, by placing a Reverse-Flash costume inside his ring. He appears briefly in Flashpoint #1, telling Barry's mother how nice it is to see her alive again. He returns in Flashpoint #4, confronting the Flash after Billy Batson is killed. He tells the Flash what really happened. Allen travels back in time to prevent his past self from stopping Zoom's murder of his mother and pulls the entire speed force into himself. This transforms history. He resets Barry's internal vibrations, allowing him to remember this. Zoom says this makes him a living paradox, because he is not connected to any timeline and can kill the Flash. However he is stabbed by Thomas Wayne from behind and apparently killed. Later the timeline is restored to one that is similar but not identical to the original.
Hunter Zolomon aka Zoom first appeared in The Flash: Secret Files & Origins #3.
After arriving in Keystone City, Hunter Zolomon was hired as a profiler, working with the police in their Department of Metahuman Hostilities. His work put him in constant contact with the Flash (Wally West), and the two became good friends. His insight was critical in solving cases, but he resented being stuck behind a desk.
He was severely injured in an attack by Gorilla Grodd, leaving him paralyzed from the waist down. He asked West to use the time-travelling cosmic treadmill in the Flash Museum to prevent this from occurring. West refused, saying that he could not risk damaging the timestream. Zolomon then broke into the museum and attempted to use the treadmill himself. The resulting explosion destroyed the museum (as well as his remaining sanity) and shifted Hunter's connection to time. He could now alter his personal timeline, giving the effect of super-speed.
Zolomon concluded that West would not help because, unlike Allen, he had never suffered personal tragedy. Zolomon decided that if he became the new Zoom and killed West's wife (Linda Park), this would help the Flash become a better hero.
Unlike other speedsters, Zoom's abilities lie not in speed but manipulation of time. For this reason he appears to be faster than The Flash and untouchable. This is betrayed in his speech patterns which ebb and flow at different speeds, almost entirely at random. His trademark attack is to snap his fingers creating a shockwave not just in space but across time. He uses this attack to cause Linda to miscarry.
The battle, the death of his unborn children and Linda's resultant despondency was too much for The Flash, so he enlisted the help of the Spectre (at the time, the spirit of Hal Jordan) to remove all memory from the world about the Flash's secret identity (including himself). Zoom, however, was unaffected and returned to plague him, but became trapped outside of time when he tried to join forces with Professor Zoom to make Wally relive the deaths of his children. Teaming up with the Cheetah, Zoom stretched his influence to the Justice League, but stated repeatedly that his only interest was "making the Flash a better hero". He enlists with the villainous Mockingbird (later revealed to be a disguised Lex Luthor) and is responsible for disfiguring the hero Damage.
Following a brief 'alliance' with Iris West when she requests his aid to save the Flash – now Bart Allen – from a future catastrophe, Zoom attempted to enlist Inertia as his new sidekick. However, despite Zoom restoring Inertia's speed by giving him access to his own temporal powers, Inertia soon turned on Zoom, claiming that he just wanted to make the heroes suffer where Zoom actually wanted them to work through the damage he inflicted, Inertia unravelling Zoom's timeline to return him to a powerless Hunter Zolomon.
This version of Zoom has not appeared in DC's reboot following Flashpoint.
Inertia was a clone of Bart Allen. He originally fought Allen when he was Impulse. Later when Bart aged five years after Infinite Crisis and became the Flash, Inertia fought him again. Inertia was responsible for Allen's death and when Wally West returned he took revenge by paralyzing Inertia and putting him in the Flash Museum. During Final Crisis: Rogues' Revenge, he was used by Libra and Zoom to try to get the Rogues to join the new Secret Society. He stole Zoom's powers, called himself Kid Zoom, and was killed by the Rogues, who blamed him for making them kill Bart Allen.
When questioned as to who created Inertia, Ethan van Sciver wrote that he could only accept five percent of the credit. The rest was offered to Mike Wieringo (twenty percent), Grant Morrison (twenty-five percent) and Todd Dezago (fifty percent). He also states that Inertia's appearance is just Impulse's inverted, like a Reverse-Flash. This fits the character's original role as a "Reverse-Impulse" created to antagonize the title character.
Inertia's initial appearance came in Impulse #50: "First Fool's" (July 1999), followed by #51: "It's All Relative" (August 1999). The most character development came in #53: "Threats" (October 1999). Inertia wasn't featured again until Impulse #62 and #66: "Mercury Falling" (July, November 2000). Inertia would not be notably featured again for half a decade.
Inertia then began making regular appearances, mostly due to his twin Bart Allen becoming The Flash. Inertia appeared in The Flash: The Fastest Man Alive #5: “Lightning in a Bottle, Part 5” (December 2006). Inertia acted as an antagonist to Allen.
In addition to his Flash appearances, Inertia made repeated appearances in Teen Titans (vol. 3). Teen Titans featured Inertia as part of an enemy team, Titans East. The story arc began in Teen Titans (vol. 3) #43 (January 2007). The arc concluded with Teen Titans (vol. 3) #46 (April 2007).
Inertia is primarily a speedster. He has not demonstrated any other speed-related powers, such as Bart's resilience to alterations in the time stream. For some time following Infinite Crisis, Inertia remained disconnected to the Speed Force. Instead, he injects himself with Velocity 9, a substance that helps him maintain his speed. Velocity 9 has been notoriously unstable in the past, but Deathstroke's new variant seems to offer no negative side effects. For a brief period before his death, he shares his powers with Zoom, who lends him his speed to pressure him into being a new Kid Flash. His attempt failed, Inertia turns into a maddened Kid Zoom, with absolute mastery over the individual timestream of a human being, able to revert Zoom to the powerless Hunter Zolomon before being killed by the assembled forces of the Rogues.
Daniel West appears at first in Flash #23 (of the New 52), garbed in a primarily black and red costume, as opposed to the yellow and red of previous Reverse-Flashes. Later, in Flash #23, he is revealed as Iris' brother, who received his powers from a freak combination of a Rogues attack and an incident which involved the Speed Force granting powers to several individuals. He desires to help Bart. Since in the current continuity Daniel broke his father's spine, making him a paraplegic and alienating Iris, he now desires to travel further back in time to kill his father before that incident, altering the timeline and regaining Iris' affection.
While the previous Reverse-Flashes only wore a costume, Daniel West wears armor that he can control, made from shrapnel from the Speed Force-supercharged monorail that was destroyed in the incident which gave him his powers.
In DC's Tangent Comics reality, Reverse Flash is an evil holographic duplicate of Lia Nelson (the Flash), created by a sinister government agency. She was charged with negative ionic energy to disperse Flash's photon-based form. However Flash's lightwave powers outmatched Reverse-Flash's and Reverse-Flash was destroyed. This Reverse Flash only appeared in one issue, Tangent Comics: The Flash (December 1997).
In other media
- Reverse-Flash was alluded to in the live action series The Flash (1990). In the episode "Done With Mirrors", Barry Allen temporarily takes the pseudonym 'Professor Zoom' while investigating the Mirror Master. In the episode "Twin Streaks", scientist Jason Bressell and his assistant Ted Witcome create a clone of Barry they name Pollux. Though this blue-suited character bears a resemblance to the Reverse-Flash, Pollux has no direct relation to any comic anti-Flash, instead being more along similar lines of Bizarro and lacks any true malice, instead being more childlike in his actions and mannerisms.
- In the Justice League Unlimited episode "Divided We Fall", Lex Luthor/Brainiac creates robotic copies of the Justice Lords, the Justice League's villainous alternate universe counterparts. Since the Flash of that alternate reality died before the Lords were formed, Brainiac/Luthor creates a Flash duplicate (voiced by Michael Rosenbaum) wearing the Reverse-Flash's red-on-yellow costume and acted like Zoom while fighting Flash (Wally West).
- Reverse-Flash made an appearance in the Robot Chicken episode "Losin' the Wobble" voiced by Seth Green. He is seen robbing a bank, while Flash, Superman and Wonder Woman stand idly by, commenting about how "lame" they think opposite-themed villains like Reverse-Flash, Bizarro and Negative Wonder Woman are. In the Robot Chicken DC Comics Special 2: Villains in Paradise, Reverse-Flash (voiced by Matthew Senreich) is seen with the Legion of Doom.
- In the 2014 TV series The Flash, the Reverse-Flash is a character named Dr. Harrison Wells and serves as the main antagonist of the first season. A flashback to Barry Allen's childhood reveals he killed Barry's mother Nora by stabbing her in the heart. It is later revealed that the Reverse-Flash was battling an older Barry Allen from the future. He resurfaces fourteen years later, attacking Joe West and threatening his daughter in order to halt his re-investigation of Nora Allen's murder case. Shortly after, he attacks Mercury Labs to steal Tina McGee's tachyon device in order to, as revealed later, to stabilize his wavering powers. He confronts the Flash and the police, easily defeating them. This incarnation possesses a yellow suit like others but his legs and lower arms are black, and emits red lightning when he runs. The Reverse-Flash (or at least one of them as of right now) is Dr. Harrison Wells (portrayed by Tom Cavanagh), Barry's mentor and head of S.T.A.R. Labs, he has super speed that radiates red lighting off of him whenever he utilizes that power too. Although Harrison may have a form of super speed, his power can only go so far due to it timing out since it's not fully stable, causing him to have to habitually recharge it by using the tachyon device to harness energy. Recently, Cisco Ramon's blood tests couldn't prove that Wells is the Reverse-Flash that killed Barry's mother, which makes him another yellow-donned speedster since Dr. Wells has been verified to be one version of the persona.  In the episode "Fallout", Harrison Wells reveals himself as Reverse-Flash to General Wade Eiling after kidnapping him from his army base.
- The Professor Zoom version of Reverse-Flash is the main antagonist in Justice League: The Flashpoint Paradox voiced by C. Thomas Howell. This is notably the first appearance of a Reverse-Flash as an individual character rather than an evil duplicate from previous appearances. Inertia also appears in the movie as a display inside the Flash Museum.
- Zoom appears in the Game Boy Advance and Nintendo DS game Justice League Heroes: The Flash as the fourth level boss.
- Professor Zoom's Black Lantern appearance is an alternate skin for Flash (Barry Allen) in the video game Injustice: Gods Among Us.
- Professor Zoom appears as a playable character in Lego Batman 3: Beyond Gotham.
- Blur, a White Martian/Human hybrid who appeared in the Son of Vulcan mini-series.
- Züm, a White Martian with super-speed and member of the Hyperclan.
- Johnny Quick, the Flash's evil counterpart from the anti-matter Earth.
- List of Flash enemies.
- "Inertia . . . ! - Page 4 - The Comic Bloc Forums". Comicbloc.com. Retrieved 2011-04-25.
- Raftery, Liz (January 8, 2015). "The Flash Will Introduce Reverse Flash – But Is There Just One?". TV Guide. Retrieved January 8, 2015.
- Crimson Lightning - An online index to the comic book adventures of the Flash.
- Justice League Unlimited at the Internet Movie Database
- The Flash at the Internet Movie Database