As Oliver and Felicity attempt suburban, domestic bliss, Star City is being targeted by an elite group who are outmaneuvering Team Arrow at every point, forcing Oliver to return and take up the mantle of Green Arrow.
Tropes in Arrow Season Four include:
- Bittersweet Ending: The team ends up saving the city, and the world, from nuclear annihilation, and Oliver kills Damian Darhk, thus getting justice for Laurel's death. He also ends up becoming the symbol of hope for the city he wants to be, and is even appointed Interim Mayor. However, Team Arrow effectively disbands - with Lance leaving town after losing his job in the SCPD to mourn Laurel's death, Thea leaving the team just to cope with the accumulated traumas of the past year, and Diggle leaving not only the team but his family as he takes some time off to come to terms with the fact that he murdered his brother in cold blood. Though it's implied the disbanding is only temporary so they can have time to cope.
- Came Back Wrong: Thea starts to act irrational and violent, later deduced to be a side-effect of her revival with the Lazarus Pit. The pit is later used to bring Sara back, which is especially dangerous as it's usually not done for a complete resurrection. Sara is animalistic for multiple episodes until getting her soul returned.
- The Cape: After seeing how little The Arrow was able to protect Starling City from Ra's al Ghul and even a gangster like Brick, Oliver wants to used the new Green Arrow name to actively inspire hope. He hits a wall when he realizes he can't do that if his entire motif is popping out of shadows.
- Comic-Book Movies Don't Use Codenames: Now firmly averted. Not only do Oliver, Laurel and Thea use their authentic comic-book codenames of Green Arrow, Black Canary and Speedy regularly, but even Canon Immigrant Diggle now has his very own codename... Spartan.
- Evolving Credits: The arrow in the title card is now bright green to reflect Oliver's switch to the Green Arrow.
- Flash Forward:
- The first episode ends with a scene taking place 6 months later, with Oliver at the grave site of someone close to him and vowing to destroy the evil that killed them.
- The tenth episode, which was the first episode aired after the winter break, shows Oliver walking down from the grave to talk to Felicity, who insists Oliver must kill the monster who killed their friend.
- Hammy Villain, Serious Hero: Anarchy from Season Four really gets a kick out of seeing what people do in the absence of societal constraints. This is a stark contrast to Oliver Queen, the Green Arrow, whose main priority is restoring balance and order by removing the city's villainous underbelly. Anarchy is always giggling maniacally and bouncing from place to place while Oliver rarely cracks a smile and is very methodical in his actions.
- Heel–Face Turn: Andy Diggle after A.W.O.L.. Ultimately averted when its revealed he was playing his brother and the team all along in order to spy on them.
- Heel–Face Revolving Door: Malcolm Merlyn, par for the course. He starts the season as an ally of Team Arrow's, resurrecting Sara, trying to help Thea with her bloodlust in his own twisted way, and even saving Oliver's life in the midseason finale. However, once Oliver helps Nyssa depose him as leader of the League of Assassins (and chops off his hand!), Malcolm turns against the team, allies himself with Damian Darhk, and goes so far as to kidnap Oliver's son William; in exchange for ensuring his and Thea's safety. However, at the end of the season, he becomes a Token Evil Teammate of Team Arrow again, helping lead the evacuation as Darhk's Genesis 'ark' is destroyed.
- Idiot Ball: Team Arrow when they randomly rebuild Darhk's magic idol.
- Legacy Character: Oliver, as the Green Arrow, pretends to be one, claiming to be inspired by the 'deceased' original Arrow. Laurel as Black Canary and Thea as Speedy (essentially carrying on Roy's mantle as Arsenal) also count.
- Lighter and Softer: In a sense. The universe of the show is as dark as ever, and the stakes are as high as they've ever been - the 'lightness' comes from Oliver's new attitude to life and to his crusade - in particular, his romance with Felicity, his mission to inspire hope as both Oliver Queen and Green Arrow, and efforts to rebuild strained and/or damaged relationships with people like Diggle, Quentin or even Laurel.
- Recycled Plot: Damian Darhk and H.I.V.E.'s 'Genesis' plan is essentially the same plot as Merlyn's Undertaking from Season 1, with a much larger scale and scope. Whereas Merlyn wished to level the Glades, a neighborhood of Starling City rampant with crime and poverty, so that it could be rebuilt; Darhk wishes to do the same to the entire world through a nuclear attack that wipes out everything and everyone but his followers. This is even Lampshaded by Merlyn himself.
- Revenge by Proxy: Damien Darhk fatally stabs Laurel Lance because he made a promise to her father that if he had betrayed him, he would kill his daughter. This then set in motion for Oliver to kill Damian Darhk to avenge her death and for the others, Damian had killed.
- Shout-Out: When Felicity finally gets a codename (Overwatch) Oliver explains that he "was gonna go with Oracle, but it was taken", seemingly suggesting that Batman is indeed active in the Arrowverse.
- Sibling Team: Oliver and Thea are now this, alongside the other members of Team Arrow, of course. Sara and Laurel are also this for the episode "Lost Souls".
- So are John and Andy in their flashbacks and also during the time Andy is seemingly 'reformed' and works with Team Arrow, until he shows his true colors.
- Strong as They Need to Be: This was a noticeable problem this season in regards to Oliver. Having killed Ra's al Ghul, it doesn't come as a surprise when he absolutely crushes Malcolm Merlyn in a duel. What does come as a surprise is when he does that while having problems with the likes of Anarky this season, who should be nowhere near his level. It wasn't until Season 5 that this problem was corrected.
- Tonight, Someone Dies: See Flash Forward above.
Word of God has stated that yes, a member of the main cast would die and not come back. And they didn't. The question was, over and over, who will it be? - Took a Level in Jerkass: After his stint of being Team Arrow's Token Evil Teammate, Malcolm goes back to being their Arch-Enemy after Oliver arranges it that he loses the title of Ra's al Ghul to Nyssa as well as his hand.
- Villain Forgot to Level Grind: In Season 1, Malcolm handed Oliver his ass twice and only lost the third time due to Oliver piercing himself with an arrow so he could pierce Malcolm's chest. But after two seasons of having to face super soldiers and assassins on a constant basis, along with receiving training from both Ra's al Ghul and Malcolm himself on top of what he learned during those five years away from home, it's clear that Oliver has long since surpassed him. This is established in their duel for leadership of the League, where Oliver defeats him in short fashion and cuts off his hand. What makes it even more blatant is the fact that Ollie was holding back so he wouldn't kill Malcolm.
