With its eight seasons, Arrow has had plenty of time to build its fictional world, as well as its heroes. Even though the show primarily focused on the titular superhero Green Arrow, it also gave a lot of space to side characters which were - in more case than one - sometimes even more interesting than Oliver Queen himself.
Not all of the show's most prominent characters stand on the side of good. Some were outright villains while others moved between good and wrong, depending on the situation. Whatever the case, some Arrow actors simply did a better job than others and created truly memorable characters.
Willa Holland
Many fans of the show hated Thea Queen a little at first - because she looked and acted like a spoiled teenager. But there was more to Thea. She grew a lot during the show's run, became a warrior, and then left the superhero part of her life behind to start anew.
That must have required a lot of courage. Willa Holland was sometimes annoying, sometimes lovable in the role, just like teenagers often are in real life - and she portrayed Thea's inner pain well.
Katrina Law
The only reason Katrina Law's Nyssa al Ghul doesn't rank higher on this list is that the Arrowverse is full of amazing performances - both from actors playing superheroes and those who portrayed villains.
Nyssa is a little bit of both - she worked with the heroes multiple times but also sometimes stood against them. Katrina Law is then perfectly believable as a woman who has to decide whether to follow her harsh upbringing or build her own path and do what she wants, such as loving Sara.
David Ramsey
David Ramsey's John Diggle has been with the show from the start, and now it looks like Ramsey might be playing another part in the Arrowverse. But for now, his John Diggle is more than enough.
Diggle is the type of best friend slash sidekick any superhero could ask for, Green Arrow included. His character transformation isn't as strong as with other heroes, but Diggle is still sympathetic and fun to watch.
Stephen Amell
Some people criticized Stephen Amell for Oliver Queen's lack of expression. It's true that Oliver isn't as emotional in the show as other characters - or at least doesn't like to express his feelings. But that doesn't mean he lacks them.
Amell repeatedly demonstrated he can also capture Oliver's more relaxed and emotional moments well. And as his character evolved, so did his performance.
Colin Salmon
Walter Steele played the biggest part in the first season of the show but he also appeared later on, especially when Moira Queen stood against Malcolm Merlyn who held her husband Walter as a captive.
Colin Salmon is an experienced British actor who brings a British style of acting into the American show. He's distinguished, intelligent, and kind to Thea, all of which makes him a side character who deserved more space on the show.
David Nykl
The Czechoslovakia born actor David Nykl played a recurring part of Anatoly Knyazev on Arrow. Anatoly was sometimes a mentor and a good friend to Oliver, sometimes his enemy. Even though he was a member of the Bratva, a criminal organization, Anatoly was, at his core, a decent and friendly guy.
Nykl managed to balance both sides of his personality - the man who gets rid of his enemies, and the guy who does shots with Oliver Queen.
Manu Bennett
Not every actor can start his role as a hero, then go to become a villain, and sometimes switch in between. Slade Wilson aka Deathstroke is one of the most complex characters of Arrow, and also one of the show's best villains.
He was Oliver Queen's friend and mentor before they injected him with the Mirakuru serum, and Slade eventually succumbed to insanity and thirst for revenge.
John Barrowman
Some of the best characters on Arrow were those who oscillated between good and evil. Malcolm Merlyn, portrayed by the well-established Scottish actor John Barrowman, is one example of that. Malcolm Merlyn leads a double life, he seems like a rich businessman but in fact, he's a member of the League of Assassins.
Merlyn likes to manipulate people, but he cares about his daughter, and the list goes on. John Barrowman brought a lot of charm to the role, as well as deep emotions.
Paul Blackthorne
Paul Blackthorne's Quentin Lance is the one character many fans believed deserved better. Quentin hasn't had an easy run on the show, he faced multiple tragedies, most notably the deaths of his daughters (multiple times).
Paul Blackthorne excelled at portraying Lance's various emotions that ranged from happy to absolutely miserable... not to mention Lance's alcohol addiction which he also battles on the show.
Susanna Thompson
Moira Queen wasn't always one of the good guys - but that didn't make her less sympathetic. Everything Moira did, she did for the good of her two children, even if it meant she sometimes did unsavory things.
Moira Queen's complex character would be a challenge for any actress, but Susanna Thompson did an excellent job portraying Moira's duality, the fact she was torn between right and wrong, heroes and villains.