From the very first episode of Season 4, Arrow began teasing an important death for the good guys. A flashforward in the premiere featured Oliver declaring vengeance against a mysterious "him" while shedding a few tears over a headstone.
It wasn't hard to figure out that the death had to be somebody major on the vigilante scene, and the only Flarrow-verse characters who would be ruled out were Oliver Queen, Barry Allen, and eventually Felicity Smoak. The person to die would have to be a big enough presence in Oliver's life to move him to tears and a quest for vengeance, but not so major a character that the show couldn't survive his or her death.
Well, it was seventeen episodes before we found out who was to die: the Black Canary herself. Laurel Lance was murdered by Damien Darhk, and the show will never be the same now that she is out of the picture. It's not entirely easy to imagine an Arrow without Laurel; now that Season 4 has come to an end and showed what Arrow will look like without her as a member of Team Arrow, however, it's safe to say that her death was objectively a good thing for Arrow as well as the other two shows in the Arrow universe on The CW.
Here are six reasons why her death - however sad it may have been - in Season 4 will work out for the greater good in Season 5 and beyond.
6. Too Many Death Fakeouts
Arrow developed the unfortunate habit over its first four seasons of not keeping dead characters dead. The Dark Archer - AKA Malcolm Merlyn - turned out not to be dead. Sara Lance comes back from the dead all the time. Slade was never dead. Ray and Roy only seemed dead. Oliver wasn't even dead after being skewered and kicked off a mountaintop. Thea was brought back from certain death thanks to a magical pool of resurrection juice. Andy Diggle hadn't actually been killed in action. The show had established a world in which "dying" doesn't necessarily mean being gone forever, and that was a status quo that completely ruined the stakes for a lot of the conflicts. The danger didn't feel as real if resurrection was a possibility.
Laurel's death was established right away as one that is sticking. Nyssa even confirmed to Quentin that there are no more known Lazarus Pits that could be used to bring her back, and magic was never seriously explored as an option for undoing her death. Arrow killed Laurel with no clear intention on bringing her back, and the stakes are nice and high for the good guys in Star City once more.