With CW's The Flash approaching the end of its eight-season run (June 29th), there has been a wide array of appearances from many different characters throughout the DC Universe. Whether they were fellow heroes from other shows, menacing villains, or just there to provide support for our heroes, these characters found a way to make an impact on the show and provide memorable appearances that fans will never forget.
Some of these characters didn't get the privilege of having their own show or even multiple episodes and were forced to just make do with the screen time they had. However, while only appearing in one episode there were definitely some characters who were able to stand out as some of the show's best.
Turtle (Season 2, Episode 10)
Despite the silly name, the Turtle proved to be one of the more interesting villains in The Flash. Having powers that directly contrasted the scarlet speedster, the Turtle was able to serve as a more unique challenge for the Flash to face off against.
Having comic book ties with the Flash that go all the way back to the Golden Age, the Turtle serves as one of the most iconic DC characters that do the comics justice. Unfortunately for fans, he would eventually meet his end at the hands of Harrison Wells, and it was a pity that only one episode is what the show would have in store for the Turtle.
Atom Smasher (Season 2, Episode 1)
Albert Rothstein aka Atom Smasher started the season off with a bang as being the first multiversal villain introduced in the show. Having both super strength and the ability to grow in size, Atom Smasher became one of the most physically imposing villains in The Flash, thus far.
Atom Smasher provided fans with the brawn vs. brain (and superspeed) matchup that kept fans on the edge of their seats. Despite only having one episode, Atom Smasher proved to leave his mark on the franchise, and leading the show towards the idea of multiple realities is something that would change not just The Flash, but the entire future of the Arrowverse.
Black Canary (Season 1, Episode 19)
While not having much screen time in the episode, Laurel Lance definitely left her mark as one of the biggest and most surprising cameos of the show's inaugural season. When talking to Laurel in private, Cisco has an adorable fanboy moment when Laurel reveals her identity as the Black Canary and asks for upgrades to her sister's sonic device.
Watching Cisco absolutely obsess over Laurel was funny enough for fans in its own right, but seeing Laurel obtain her signature ability: The Canary Cry, causes Black Canary's appearance in The Flash to be one of the best.
Trajectory (Season 2, Episode 16)
As the first female speedster to make an appearance in the show, Trajectory quickly shocked fans by outrunning Barry Allen in their first confrontation. A newcomer to the Speed Force, Eliza Harmon/Trajectory was a scientist who gained superspeed after injecting herself with Velocity-9, but quickly became corrupt with her addiction for more V-9.
After losing to Flash in the episode's climax, Eliza turns down Barry's offer for help and instead injects herself with more V-9 causing her to disintegrate as she speeds off with blue lightning. Seeing the tragedy of a well-intentioned scientist turned addict to her own experiment gone wrong provided fans with one of the most interesting Flash villains whose time on the show was much too short.
Vandal Savage (Season 2, Episode 8)
The immortal madman Vandal savage makes one of the most out of nowhere appearances in all of the Arrowverse. Literally crashing the Team Arrow/Flash reunion by crashing through a window, Savage was able to go toe-to-toe with Oliver Queen and even injured Barry Allen.
Despite having no actual superpowers of his own, Savage provided the show with a ruthless and cutthroat villain who relied on nothing but skill and evilness alone. Though it's now evident that the episode served as a way to set up Savage as the main villain for DC's Legends of Tomorrow, that doesn't take away from him shining as one of the best villains in a Flash episode thus far.
The Ray (Season 4, Episode 8)
Ray Terrill was one of the biggest surprise appearances in the "Crisis on Earth-X" cross-over. He immediately intrigues the audience as he is about to be executed for his forbidden love of Leonard Snart. Teaming up with the Flash to take on Red Tornado, The Ray adds a very interesting dynamic to the episode.
While fans can't get enough of superhero fights in general, seeing The Ray who stands as a light in the darkness of Earth-X's harsh reality makes him a powerful, inspiring symbol that fans can resonate with. In also paving the way for future LGBTQ heroes, it's no question that The Ray was one of the best standouts on The Flash thus far.
A.M.A.Z.O. (Season 5, Episode 9)
Perhaps one of the strongest villains in the entire Arrowverse, A.M.A.Z.O. was strong enough to take on the likes of Superman, Supergirl, Flash, and Green Arrow. The super-powered android was a main antagonist in CW's "Elseworlds" crossover and had the ability to copy the powers of other superheroes.
Aside from the excitement from comic book fans already familiar with A.M.A.Z.O., the appearance of the android reset the bar for future villains in the Arrowverse. Though A.M.A.Z.O. would only appear in one episode of The Flash, the robot definitely left its mark on not just the show, but the entire Arrowverse.
Lewis Snart (Season 2, Episode 3)
Lewis Snart makes one of the most intriguing appearances in the earlier seasons of The Flash as it is revealed he is the father of Leonard Snart (Captain Cold) and Lisa Snart (Golden Glider). Being both an abusive father and a menacing villain overall, the introduction of Snart allowed fans to get a glimpse of what growing up in the Snart house was like as a child.
Seeing the abuse that the two villains went through as children proved to build sympathy amongst the audience and even greater disdain for their father as a truly evil villain. In just one episode, the father of the Snart children proved that you don't need powers to be a menacing villain.
Clyde Mardon (Season 1, Episode 1)
When the show first began, Clyde Mardon has the honor of being the very first villain of The Flash. After the particle accelerator explosion grants Mardon the power to manipulate weather, an epic battle with the scarlet speedster ensues that sees Flash reach speeds of 700 mph in order to take the villain and his F5 tornado down.
Being both menacing and obsessed over his new self-image now that he has powers, Clyde Mardon embodies what it means to be a Flash villain and set the bar for the villains to come. His vicious yet quirky over-the-top nature made for a perfect opening series villain, and though the original Weather Wizard for sure wasn't one of the most threatening villains, he definitely could've been one of the show's most iconic.
Music Meister (Season 3, Episode 17)
In what is by far one of the most unique episodes of The Flash, Music Meister is able to effortlessly take down the likes of Flash and Supergirl. What's even more interesting though, is that the seemingly omniscient being chooses to send Barry and Kara's minds to an alternate dream-like reality where they are living inside of a musical to teach them a lesson about love.
While his methods may be far from practical, Music Meister's silly and cheesy nature was able to save both Barry and Kara's respective relationships and gave fans the cross-over they never knew they wanted. While it's a shame Music Meister never returned to show off more of the singing prowess of the Arrowvere's heroes, it's safe to say the character definitely made the most of his only episode.