Oliver Queen killed a lot of people throughout the first season of Arrow in his first steps towards becoming the hero known as the Green Arrow. Throughout the eight seasons the show went on, the billionaire playboy went from being a spoiled brat that washed on the shores of a mysterious island to a cold-blooded killer that discovered the true meaning of justice and only killing when it was completely necessary.
Oliver learned how to seek justice the right way and the show did a very good job of showing his journey in becoming a hero through the flashbacks up to the present day. Some of Oliver Queen's kills can be justified, others can't be as they weren't crucial to his survival and were more so just him seeking revenge or taking justice into his own hands. Here's 5 times Oliver Queen's killing was justified and 5 times that it wasn't.
Justified: Ra's Al Ghul
This one could definitely be justified as Oliver was left with no choice but to put an end to the man that was going to take down his city. Unlike with Slade Wilson, Ra's Al Ghul had far more resources and posed a huge threat considering the amount of power he had.
If he had spared Ra's, it's possible he could have just rose to power once again and Oliver's effort to stop him would have been for nothing. Ra's defeated Oliver on the mountaintop and left him for dead, this is simply just returning the favor for the greater good.
Not Justified: Justin Claybourne
This one is kind of tough considering that Justin Claybourne was a very terrible man and did horrifying things just for profit such as infecting people with an illness. Oliver tried to turn him and get Claybourne to do the right thing but he wouldn't listen. He then kills Claybourne without hesitation and ultimately creates the villain Prometheus that would come for him years later.
It is said later in the season that Claybourne wasn't necessarily too fond of his son that becomes the villain. However, instead of murdering Claybourne, Oliver could have let the man face a trial and jury.
Justified: Masked Men
The pilot of Arrow did a really great job of showing the beginning of Oliver Queen's journey in becoming the hooded vigilante. This episode paints him as a cold-blooded killer. Oliver and his best friend Tommy Merlyn find themselves abducted by masked men trying to get more information on how much Oliver knows about the sabotaging of the Queen's Gambit.
Now a force to not be reckoned with, Oliver kills the masked men easily. Specifically for the reason of not wanting them to tell people about his new crime-fighting abilities. This one can definitely be justified as these men acted first and seemed to be willing to kill Oliver. While he could have probably just knocked out the masked men, Oliver did what needed to be done to protect himself and Tommy.
Not Justified: Corrupt Cop
This scene in the first episode of Season 5 is basically a repeat of the abduction scene from the pilot. This time around, Oliver is now the Green Arrow and the Mayor of Star City. This one really can't be justified considering Oliver has already been proven to not be the Hood or even a vigilante.
There was a very slim chance that the corrupt cop would have come to that conclusion. He could have just knocked him out and turned him in rather than go back to killing. It was a cool scene and a huge callback to the first season but really just seems like Oliver enjoys killing the cop rather than doing it to survive.
Justified: Damien Darhk
Just like Ra's Al Ghul, Damien Darhk posed a huge threat to Star City and Oliver was left with no choice but to put an end to him for good. Especially after the death of Laurel Lance, this was a satisfying end for the villain.
Although the fourth season was very strange and was a huge change for the series, it was very cool to see Oliver use mystical abilities to take down Damien Darhk. The threat was just way too big and the stakes were way too high for Oliver to have spared Darhk. The villain was however resurrected for the spin-off show, Legend of Tomorrow.
Not Justified: Leo Mueller
A lot of Oliver's kills in the first season can't be justified as rather than survival, he's mostly just crossing names off a list that his father left him. He takes the justice upon himself and Leo Muller becomes a victim of that. Muller is, of course, a bad man but he deserved to be taken down using the law rather than being murdered by the Hood.
There was a choice here and murder shouldn't have been the only option on Oliver's mind. Some of the best episodes in the series saw Oliver dealing with the repercussions of his actions as a cold-blooded killer, thankfully this didn't result in anything bad.
Justified: Edward Fyers
Oliver's first major kill at the end of the first season sees him kill Edward Fyres after he captures his friend, Shado. He offers Oliver a chance to go back home which is what he's wanted since he washed up on the shores of the Island.
However, Oliver is now a changed man and going back home isn't a priority over his friends. He fires an arrow to save Shado and puts an end to Fyres for good. His face during this shows just how much he's changed as he doesn't seem to show any bit of fear or even feeling while killing Fyres.
Not Justified: Billy Malone
While this one was by accident, it's still Oliver's fault for going straight for the kill rather than confirming the identity of the man behind the mask. His rage and impatience clouded his judgment and he ends up killing an innocent man which happens to be Felicity's boyfriend at the time.
Prometheus is definitely to blame as well for setting Oliver up but he wasn't the one that shot the arrow. Oliver should have found it strange that the man he shot out was so out in the open and not have acted impulsively.
Justified: Konstantin Kovar
This one can be justified considering it was a life or death situation and Oliver was running out of time for his short time frame to be saved by the boat off the shore.
Kovar would have killed Oliver there or hunted him later on if he would have spared him and it's possible that he could have revealed his identity as the Hood considering it wouldn't be too hard to connect the dots. Although this was initiated in the first place by Oliver, this was necessary for his survival.
Not Justified: Anthony Ivo
This one was more for revenge rather than true justice. Although it was definitely not the worst choice for Oliver to make considering that Ivo killed Shado, the man was already going to die.
Slade hated him just as much as Oliver and there was no way he was going to make it out alive. If Oliver really wanted to kill him so badly, it would have been wise to maybe do it before Slade discovered the truth of Shado's death. It could have possibly prevented their fallout. This was part of Oliver's transition into a cold-blooded killer and it can't be justified as it really wasn't part of his survival.