While it wasn't the first DC show to hit The CW, The Flash soon eclipsed Arrow as one of the most beloved. This was probably due to the fact that it didn't take itself as seriously as its predecessor, but still maintained that important link to the Arrowverse. The big thing about The Flash, as well, is the show's refusal hold back when it comes to the bad guys that the speedster has to face.
While Arrow has plenty of bad guys, many of them are based on real-world ideas. Meanwhile, Flash battles everyone from time travelers to giant apes to evil versions of himself, keeping it fun every step up the way. Let's take a look at some of the best villains in the show's history.
10 King Shark
Honestly, if Gorilla Grodd hadn't come first, maybe King Shark would be ranked higher. It is amazing what The Flash is able to do with its budget when it comes to these monster villains. King Shark is Shay Lambden from Earth-2, who was hired by Zoom to take out Flash. He was beaten and imprisoned at A.R.G.U.S.
His story got interesting when Team Flash began working on a cure for the meta-humans. He was able to finally get cured, but passed up the chance when Gorilla Grodd escaped and Team Flash needed King Shark to battle the giant villain. It was a nice moment where Shay gave up his chance to be human again to do something good to help the world.
9 Wade Eiling
Wade Eiling was supposed to be a good guy. A general who was tasked with helping protect America, no less. However, Eiling was as corrupt as they come, and his goal was never to do the right thing. Instead, he wanted to use any meta-humans created after the particle accelerator explosion to form his own army of superhumans.
Gorilla Grodd became such a dangerous villain because Eiling committed inhumane experiments on the creature. Eiling himself was more of a nuisance to Team Flash, but he did cause serious problems at times (including trying to capture Firestorm and battling the heroes under the control of Grodd).
8 The Thinker
The Thinker is Clifford DeVoe, who served as the main villain of season 4. His power --gained from the particle accelerator explosion-- was superhuman intelligence, but, unlike others, he did not have his genes altered. His abilities also allowed him to transfer his consciousness into the bus metas and siphon their powers.
Through this process, he started to stockpile numerous powers, making him one of Flash's most powerful adversaries. However, due to his increasing intelligence, he lost his ability to empathize with others and soon began to grow unstable, leading to an arrogance that resulted in his defeat.
7 The Trickster
Mark Hamill played The Trickster twice. First, he was Trickster in the classic CBS television series in the 1990s. Then, on The CW's The Flash, he reprised his role. On Earth-1, he was Central City's greatest criminal (before the particle accelerator created all the meta-humans) and was in prison by the time the show started.
He was a master manipulator, to the point where he could convince anyone to do anything he wanted them to. According to Joe, this made Trickster more dangerous than villains with conventional superpowers. Unlike his comic counterpart, this Trickster is very similar to Joker, which is ironic since Hamill also voices Joker in the animated world.
6 Killer Frost
With all the alternate takes on Earth, The Flash was able to play around with reality, asking "what if" questions concerning the characters. In the case of Killer Frost, this Flash villain was Caitlin Snow from Earth-2. This was a very interesting proposition, since Caitlin on Earth-1 was one of Barry's closest allies.
Killer Frost has the power to unleash frozen air from her hands, and was a powerful ally of Zoom's from Earth-2. While that version is gone, Caitlin from Earth-1 now has the same powers, and fans are wondering if she is fated to one day end up as the evil Killer Frost on this Earth as well.
5 Captain Cold
Captain Cold and Heat Wave were two of Flash's earliest villains on the series. While both men have gone on to have careers as time traveling anti-heroes on Legends of Tomorrow, Captain Cold was one of Flash's most complicated antagonists.
When working as villains, they were never as deadly as others, preferring a criminal career of petty thievery. When it comes to the rogue's gallery in Flash comics, many of them had a no-kill mantra, and Captain Cold demonstrated this on the TV show: he wasn't an evil man, just a bad guy. As fate would have it, he wasn't even that bad either in the end.
4 Gorilla Grodd
When The Flash revealed that it was bringing Gorilla Grodd to the small screen, a lot of fans doubted it would work. After all, Grodd is a giant gorilla --with a genius level intellect-- who can control the mind of others. It could have ended up comical and embarrassing, but instead ended up an incredible creation for the TV series.
At the start, he was a tragic villain, as Wade Eiling had committed experiments on Grodd in the name of science. When people like Caitlin tried to use him as a test subject, it awakened all kinds of bad memories, resulting in Grodd becoming one of the most violent and dangerous villains in DC history.
Savitar showed up in season 3 and was the main villain throughout. As the third speedster villain in a row, the identity of this man was kept secret for much of the season. With the bad guys in the first two seasons proving to be surprising reveals (thanks to the alternate Earths), the mystery of who Savitar was almost overshadowed how dangerous he was.
It turned out that Savitar was none other than Barry Allen himself from an alternate future. For comic book fans, this was a version of Future Flash. Being Barry from the future, he knows everything about himself, including how to destroy Barry as retribution for his "playing God" with the timelines.
The villain in season 2 was Zoom. Much like season 1, this villain was a speedster who turned out to be one of Barry's mentors. In this case, it was Jay Garrick, a Flash from an alternate Earth who helped teach Barry a lot about the Speed Force and his powers. However, there was another twist: this was not actually Jay at all, but Hunter Zolomon, a speedster from Earth-2 who stole Jay's identity.
The entire purpose of Hunter helping Barry was to increase his speed, so that Hunter could steal it for himself and become the fastest speedster on any Earth. In the end, it was Zoom who caused so much pain for Barry that he created Flashpoint, which, in turn, created Savitar. Hunter faced the ultimate fate when Time Wraiths transformed him into the Black Flash.
1 Eobard Thawne
The first villain from The Flash remains the best. That would be Eobard Thawne, the Reverse Flash. The biggest twist of season 1 was that this was Barry's closest ally, Dr. Harrison Wells, the director of S.T.A.R. Labs. The entire story was set up when Thawne recreated the accident that created Flash, giving himself powers, only to learn that he was destined to become Flash's arch-nemesis.
Eobard killed Barry's mother and framed Henry Allen for the crime, then ended up trapped in the 21st century. There, he took on the identity of Wells. It wasn't just his powers as a speedster that made him Flash's greatest villain, but the manipulative methods he used to try to destroy Barry's life from the start.