Following the contemporary trend of interconnected superhero franchises, the CW has spent the last decade building up the Arrowverse with shows such as Black Lightning, Supergirl, and Superman & Lois. However, as successful as the subsequent additions to the connected universe have been, all the best episodes in the Arrowverse, at least according to IMDb, have come from the first two Arrowverse shows, Arrow and The Flash.
It is no surprise that many of the episodes that most resonated with fans are the bigger event episodes, such as Arrow's big team-up fight against Adrian Chase in "Lian Yu" or the conflict between the two heroes in the season 1 episode of The Flash, "Flash vs. Arrow."
The Flash - "Flash Vs. Arrow" (9.3)
In the season 1 episode "Flash vs. Arrow," Oliver, Diggle, and Felicity travel to Central City in pursuit of a criminal. While there, Barry falls victim to Roy Bivolo's powers and ends up becoming rageful and aggressive, leading to a showdown between Arrow and the Flash.
Considering how early on in the show this episode occurred, it was one of the first and best Arrowverse crossover episodes that delivered on the franchise's potential by delivering a fun episode and memorable fight between the two heroes.
Arrow - "The Slabside Redemption" (9.4)
As the title suggests, the season 7 episode "The Slabside Redemption" revolves around a prison break and Oliver's eventual release from Slabside Maximum Security Prison. When Diaz is transferred to Slabside, he releases all of the prisoners and creates a riot, leading to a violent confrontation with Oliver.
Tense and action-packed, the episode is a satisfying conclusion to the Slabside story arc. Oliver has always been one of the bravest characters in Arrow and watching him take on an entire prison's worth of criminals only confirms that.
The Flash - "The Trap" (9.4)
The 20th episode of season 1, "The Trap," sees Barry and his team try to lure Reverse-Flash into a trap. Reverse-Flash, however, is one step ahead of the heroes, escapes the trap, and takes Eddie hostage.
The episode is full of exciting twists and reveals as Gideon informs Barry about important moments from his future and Iris learns that Barry is the Flash. Additionally, the episode helps further prove that Reverse-Flash is one of the smartest and most powerful villains in the entire Arrowverse.
The Flash - "Enter Zoom" (9.4)
After his introduction earlier in season 2, Zoom makes his presence known in the episode "Enter Zoom." When Barry and his team try to ambush Zoom, they underestimate his speed and he is able to defeat Barry, leaving him temporarily paralyzed and powerless.
Barry has experienced awful things in the Arrowverse, but the beating and psychological damage that he suffers at Zoom's hand is among the worse and the result is a dramatic and thrilling episode that ranks as one of the best.
Arrow - "Unthinkable" (9.5)
The season 2 finale, "Unthinkable," sees Oliver and his team take on Slade and his army. The episode is filled with memorable moments as Nyssa al Ghul kills Isabel, Diggle enlists the help of the Suicide Squad, and Oliver takes down Slade.
Season 2 is one of the best the Arrowverse has ever produced as it expanded the Arrow mythology while showcasing Slade as the series' best villain. "Unthinkable" is the perfect ending to this groundbreaking season, delivering on the highly anticipated showdown between Oliver and Slade.
Arrow - "Sacrifice" (9.5)
The first season of Arrow builds to a climactic showdown between Oliver and Malcolm Merlyn, who plans to level the Glades in the season finale, "Sacrifice." The action-packed episode sees Thea and Roy trying to save people in the collapsing Glades, Tommy sacrificing himself to save Laurel, and Oliver and Diggle seemingly killing Malcolm.
Arrow's first season laid the groundwork for the Arrowverse and the season finale managed to completely stick the landing, bringing the season to a compelling conclusion filled with dramatic moments that deeply impact the characters.
Arrow - "The Climb" (9.6)
"The Climb," a season 3 episode, pays off the investigation into Sara's murder by revealing that Thea had killed her while under Merlyn's influence. The episode also includes Oliver's fight against Ra's al Ghul and Ray taking the next steps towards becoming Atom.
In addition to further developing great supporting characters like Thea and Ray, the episode also features the standout fight between Oliver and Ra's al Ghul. While fans knew that the show would not actually kill off Oliver in the episode, watching him meet his match is a shocking and thoroughly entertaining moment and a great cliffhanger.
The Flash - "Fast Enough" (9.6)
Bringing season 1 to a close, the season finale "Fast Enough" sees Barry learn the truth about his mother's death at Reverse-Flash's hands, prompting him to create a wormhole to return to the past to save her before being warned not to by a future version of himself.
Ending with a massive cliffhanger as Barry runs into a black hole, the episode is full of shocking moments like Eddie's sacrifice to wipe our Eobard. It is a great conclusion to one of the best seasons of any superhero show ever.
The Flash - "Out Of Time" (9.6)
The season 1 episode "Out of Time" features the revelation that Harrison Wells is actually Reverse-Flash. After Iris learns that Barry is the Flash and Thawne kills Cisco, Barry runs faster enough to turn back time while trying to prevent a tsunami created by Mark Mardon from destroying the city.
The episode's ending is reminiscent of classic DC stories like the first Superman movie. The episode also furthers the complex and compelling relationship dynamic between Barry and Thawne. It captures the essence of the character and everything that fans love most about the show.
Arrow - "Lian Yu" (9.7)
The season 5 finale, "Lian Yu," features some of the show's biggest and most dramatic action sequences as Oliver and his team battle against Adrian Chase and his supporters on an island rigged with explosives.
Benefitting from a dramatic cliffhanger ending that leaves many of the characters' fates in jeopardy, a great balance of character moments and action, and Adrian's shocking death that sets off the explosives, it is not hard to see why "Lian Yu" is the best-rated episode in the entire Arrowverse.