Arrow launched a new era of DC television, and it had a strong eight seasons full of Green Arrow action that often stayed admirably faithful to the comic books. It featured many Green Arrow foes from the comics such as Deathstroke, the Dark Archer, Count Vertigo, Damien Darhk, and Brick. It really covered many of the highlights from Green Arrow comics and was able to impress even the most diehard of Green Arrow fans.
That said, Green Arrow comics possess a deep and rich well of memorable antagonists that could have made it to the Arrow series. Now that the show is over, we are only left to reflect what it would have been like to see these rogues pop up in Arrow's rendition of Star City.
10 Death Dealer
This Royal Flush Gang-meets-Kanto reject only enjoyed a brief stint as a Green Arrow antagonist, but his killer outfit is enough to set him apart in the annals of Green Arrow history. Like the Royal Flush Gang, playing cards are his theme. He uses them as weapons in a manner akin to Bullseye or Gambit (though he predates the latter character).
He troubled Ollie a couple of times before being killed by Cupid as a profession of love. He may not be a Star City bigshot, but it would be worth it to see that costume on the TV screen.
9 Big Game
Big Game is another small-time Green Arrow rogue that would have been nice to see in Arrow. There have actually been two Big Games: the first existed only to be killed by Cupid during her rampage. The latter was the original's son who was out for revenge.
He styles himself liked Kraven the Hunter, and he could have been a fun antagonist for Ollie or an interesting complication in Ollie's fight against Cupid.
8 Electrocutioner
Electrocutioner was always a bit of a loser as well, but he existed in an interesting place in the Green Arrow canon. Lester Buchinsky inherited the Electrocutioner mantle and costume after his brother was killed. He intended to be a lethal vigilante in the vein of, well, the Vigilante or the Punisher. He would execute criminals like a walking electric chair.
After a clash with Batman and Robin, he became a common super-criminal. He later entered the employ of Prometheus, which would later lead him to be killed by Arsenal after Prometheus' attack on Star City. Electrocutioner could have entered Arrow canon as a would-be vigilante himself, or he could have been important cannon fodder for a greater story.
7 Natas
Natas brings this list to the realm of less simply "fun" and more serious and deadly foes. Natas was a deadly assassin and even trained the renowned Deathstroke the Terminator. He also helped train Oliver Queen after a major defeat forced him to retreat from Star City.
His training of Oliver Queen was underhanded, and it often seemed that he was actually trying to kill Ollie. Despite this, Ollie came out the other side of this a better hero and returned to Star City to take on Deathstroke himself.
6 Brick (But For Real This Time)
Brick did enjoy some spotlight in Arrow, but it was a far cry from the Brick we know in Green Arrow comics. Beloved character actor Vinnie Jones portrayed Brick as something of a Kingpinesque crime boss who was also a tough fighter himself.
The comic book iteration of Brick is a metahuman who is actually made of a stone-like material. He ran the Star City underworld for a while and even tried to keep the peace after Merlyn and Doctor Light destroyed much of the city. He also seemed to be killed by Cupid but actually survived the attack. In the New 52, he was reimagined as a katana-wielding deadly warrior who worked alongside Richard Dragon.
5 Doctor Light
Arthur Light is a DC antagonist with a long and sordid history, and he's thrown down with Green Arrow plenty of times. A reimagined version of the character as Linda Park appeared in Flash, but seeing Arthur himself popping up to trouble Oliver in Arrow would have been awesome.
Doctor Light can manipulate and control light, shoot energy blasts, create Green Lantern-like energy constructs, and fly. As stated above, he and Merlyn destroyed Star City, and that means he will always have a special place on Green Arrow's enemy list.
4 Cheshire
Cheshire, aka Jade Nguyen, is among the most memorable of DC assassins as well as a renowned member of the League of Assassins. She is an incredibly-skilled fighter who is known to wield some of the most exotic and deadly toxins on Earth.
She also had a child with Roy Harper, the death of which in the destruction of Star City led to Arsenal's rampage. Cheshire has always had a sadistic yet charming personality and a vicious sense of humor, and she would have made a great addition to the Arrow rogues gallery.
3 Prometheus (But For Real This Time)
While there was a version of Prometheus in Arrow, he came off as nothing more than another Dark Archer-type character akin to Merlyn and Komodo. The Prometheus of the comics has an insanely over-the-top costume, an arsenal of deadly and often bizarre weaponry, and a bloodlust on par with few other DC rogues.
He was intended to be a sort of anti-Batman whose criminal parents were killed by police officers, and he brought the entire Justice League to heel during his villainous career. During the "Cry for Justice" story, Prometheus was killed by Green Arrow at the height of the villain's rampage, and this led Ollie down a dark path that left his life in ruins.
2 Lady Shiva
While Lady Shiva hasn't often been a common foe for Green Arrow, she is a major part of the League of Assassins and is arguably the most deadly of their numbers outside of Ra's al Ghul himself.
Arrow dealt with Ra's and the League of Assassins on a number of occasions, and it would have been a treat to see Ollie trade blows with Lady Shiva. She is one of the world's greatest martial artists in the comic books, and she would have been quite a challenge for Ollie.
1 Onomatopoeia
Perhaps the most glaring omission from Arrow is the strange and deadly Onomatopoeia. While "Mr. Blank" was something of a fill-in for the villain in Arrow, he didn't quite reach the mark. He lacked the arsenal, the idiosyncrasies, and the fantastic costume.
He briefly appeared in the Arrow Season 2.5 comics, but he never made it to the show. This character was a memorable addition made to the Green Arrow canon during the legendary Kevin Smith and Phil Hester run, and he gave the recently-returned Ollie a run for his money. Onomatopoeia has been a threat to Green Arrow on many occasions, and it would have been great to see him in Arrow.