Spoilers ahead for Episode 19 of Arrow Season 6, called "The Dragon."
Perhaps no character on Arrow has had a more bizarre arc than Dinah Laurel Lance. The Earth-1 version of the character was a lawyer who became Black Canary after a few boxing lessons, then was killed by none other than Damien Darhk. Actress Katie Cassidy stuck around, however, thanks to the Earth-2 Laurel known as the villainous Black Siren. Black Siren is still around in Star City, and she's currently teamed up with Ricardo Diaz as he escalates his reign of terror on the innocent people of the city.
In "The Dragon," Diaz went on a spree of violence, vengeance, and murder with Black Siren by his side. Katie Cassidy has weighed in on whether there's any coming back to the good side for Black Canary, saying this:
"The Dragon" saw Black Siren get in even deeper with Ricardo Diaz, and he was more brutal than ever as the episode's flashbacks showed some of what made him the way that he is. Obviously viewers probably shouldn't root for the villainess who is the right hand of a supervillain like Diaz, and he certainly doesn't seem worthy of redemption. Is she any better? Well, judging by Katie Cassidy's comments to TVLine, she at least believes that Black Siren isn't too far gone to be redeemed.
Interestingly, the case can be made after "The Dragon" that either Black Siren only needs one big push to go straight again or that she's past the point of no return. She did show some hesitation as Diaz escalated his brutality, and I suppose it speaks well to her that she draws a line at burning people alive. Black Siren isn't quite as dark and vicious as Ricardo Diaz.
Still, that's not exactly saying much. Most people in the entire Arrow-verse aren't quite as dark and vicious as Ricardo Diaz, and she didn't exactly try to stop him. Plus, new images of Black Siren over on The Flash indicate that she's still up to her villainous ways for the foreseeable future. That said, perhaps there is redemption in store for her, if only because she has people in her life who don't want to give up on her. Oliver still has hope for her, and Quentin will die before he gives up on her entirely.
Maybe the support of the good guys combined with her reluctance to do everything Diaz will do will be enough to push her out of darkness and into the light. As Katie Cassidy says, Black Siren does have a lot of explaining to do. If something traumatic happened to make her the way that she is, maybe the good guys will find it in their hearts to do anything and everything to help her redeem herself.
Or maybe Black Siren will live and die as a villain. I've actually preferred Katie Cassidy as Black Siren than Black Canary, partially because we already had a proto-Black Canary in Sara and partially because Cassidy just seems to have a lot of fun with the role. We'll have to wait and see what happens.