SPOILER WARNING: This article contains major spoilers for “The Devil's Greatest Trick,” the latest episode of Arrow.
Arrow revealed Ricardo "The Dragon" Diaz as the true villain of Season 6 in "The Devil's Greatest Trick," the latest episode. Following Cayden James' capture, Diaz paid James a visit at the Star City Police Department, where he revealed his behind-the-scenes machinations. He then proceeded to kill James in the interrogation room.
As the episode progressed, Team Arrow was successful in proving the evidence that Oliver killed Owen James false. They showed the real video to Cayden James, who acquiesced that he had been wrong but didn't relent on his plan to blow up Star City. Maintaining his ultimatum to destroy Star City, he ordered Team Arrow to bring him Earth-2's Laurel "Black Siren" Lance, Anatoly Knyazev and Diaz.
Though Team Arrow delivered, James was crazed with grief and intended to detonate the bomb anyway. A fight broke out before he was able to do that, and everyone but Oliver and his son William managed to escape. James softened at the sight of William, giving Oliver the opening to send an arrow through James' hand. After James reflexively dropped the detonator, Oliver managed to capture him alive.
Oliver dropped James off at SCPD and later visited him as Mayor Queen. Defeated, James promised to give up all the information he had on his business partners and handed over the bank account containing the money he embezzled out of Star City. Oliver then left him with the promise that he'd let him visit his son's grave.
Not long after Oliver left, the security camera in the room went offline. Diaz arrived shortly thereafter and proceeded to reveal that he was behind the death of James' son after all. What's more, he ordered the video to be manipulated so that James believed Green Arrow killed Owen. He even installed his own police chief at SCPD. He never planned to blow up the city; he simply wanted it to be weakened and left vulnerable for a takeover. So saying, he killed James right in the interrogation room. This leaves Diaz as the sole threat to Star City, as Anatoly is in the wind and Quentin is secretly holding Black Siren captive.
The episode title, "The Devil's Greatest Trick," is likely a play on the fact that Diaz was the puppet master all along. According to the full saying, "The greatest trick the devil ever pulled was convincing the world he didn't exist."
Starring Stephen Amell as the Emerald Archer, Arrow airs Thursdays at 9pm ET/PT on The CW. The series also stars Emily Bett Rickards, David Ramsey, Willa Holland and more.