The inaugural Arrowverse television series Arrow is finally coming to an end with its current and eighth season, bringing a close to the DCTV incarnation's Oliver Queen. Team Arrow has battled against many classic DC Comics villains across its eight-year run from Malcolm Merlyn to the iconic Batman villain Ra's al Ghul.

Even if Green Arrow doesn't have the deepest rogues gallery in the DC Universe, several of his villains still haven't made an appearance over the series' entire run yet. Now, we're taking a look back at some of the Arrowverse's most notable absences and looking at why Oliver never tangled against over the course of the fan-favorite television series.

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Onomatopoeia

Onomatopoeia

Created by filmmaker Kevin Smith and Phil Hester in 2002's Green Arrow #12, Onomatopoeia was a masked serial killer that specifically targeted superheroes who lacked discernible superpowers. Receiving his alias from recreating the sound effects around him, the mysterious villain is revealed to live a seemingly normal life as a suburban family man, keeping his murderous activities a secret from them.

Onomatopoeia would target both Oliver and his son Connor Hawke as part of his ongoing hunt, wounding Connor and attacking the hospital he was kept at in a bloody attempt to finish the job before being driven off by Oliver and Black Canary. Onomatopoeia would resurface years later hunting Batman on two separate occasions as one his most coveted targets.

Electrocutioner

Electrocutioner Suicide Squad

Created by Marv Wolfman, Michael Fleisher and Irv Novick in 1981's Batman #331, Lester Buchinsky was a vigilante in Gotham City that executed criminals he felt escaped proper punishment from the law with his electrified gauntlets, referring to himself as the Electrocutioner. After being defeated by Batman, Buchinsky would work as a mercenary and enforcer-for-hire, leading him to work with Prometheus.

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As part of Prometheus' plot to completely destroy Green Arrow, Buchinsky set off a device in the heart of Star City, devastating it and killing thousands, including Roy Harper's young daughter Lian. After killing Prometheus, Green Arrow began tracking down his associates responsible for the attack. Defeating Electrocutioner, Oliver is talked down from killing him by Black Canary only for Roy to kill him instead to avenge the death of his daughter.

Natas

Natas advises Green Arrow

Created by Judd Winick and Scott McDaniel in 2006's Green Arrow #66, Natas was a martial artist who trained Oliver and his extended list of allies including Black Canary, Connor Hawke and Mia Dearden after Oliver was nearly killed by a sneak attack from Merlyn. Oliver learned of Natas' vast criminal resources and defunded several of his shell companies billions to rebuild his own wealth and invest in Star City by maneuvering himself into its political scene.

In retaliation, Natas hires a squad of lethal assassins to track down and kill Oliver on a remote island, with Oliver eluding and ambushing the martial artists individually before facing off against Natas himself. Sometime later, Natas is revealed to be a former teacher of Deathstroke who frees his old master, with the two swearing revenge on Green Arrow.

Rainbow Archer

Rainbow Archer

Created by France Herron and George Papp in 1958's Adventure Comics #246, Albrecht Raines was a struggling artist that made counterfeit paintings that were noticed because of his poor use of color. After being foiled by Green Arrow, Albrecht swore revenge and trained himself to become a criminal archer, taking on the alias Rainbow Archer and employing color-coded arrows befitting his alter ego -- with the notable exception of green due to its association with the superhero that bested him.

Facing off against Green Arrow and Black Canary several times, Rainbow Archer is a lethal marksman in his own right and has partnered with various Green Arrow villains before, when not operating alone. After suffering a series of humiliating defeats, Albrecht eventually stepped back from his life of crime and into the annals of comic book obscurity.

Airing Tuesdays at 9 p.m. ET/PT on The CW, Arrow stars Stephen Amell as Oliver Queen, David Ramsey as John Diggle, Rick Gonzalez as Wild Dog, Juliana Harkavy as Black Canary, Katie Cassidy as Black Siren, Katherine McNamara as Mia Smoak, Joseph David-Jones as Connor Hawke and Ben Lewis as William Clayton-Queen.

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