In a report today on TVLine, it was said that the big bad for Arrow season 6 would be someone who is on 'many fans wish lists'. Add that to the knowledge we already have that it will be someone from Oliver Queen's past coming back to haunt him… and you get a pretty interesting list of potential characters. The problem is that the show has already tapped into his past many times with Deathstroke and Talia al Ghul. And we've now seen everything from the five years between landing on Lian Yu to being rescued. Unless they are going to add in a storyline we didn't get in the flashbacks or it's a character from before the Queen's Gambit, it seems difficult to pull from the past.
It could be somebody since he put on the hood, but that is pretty much Prometheus, and his story is actually the origin of the Richard Dragon character. I doubt they'll do that again.
A story I think that would be a lot of fun is if we find out that Malcom Merlyn had used the Lazarus Pit on Tommy Merlyn and we get Colin Donnell back, slightly crazy and wanting revenge. This would effect Oliver and Thea Queen as he is now her brother. That story can't be done though because Donnell is a regular on Chicago Med.
Another Green Arrow villain that pops up a lot in conversation is Onomatopoeia. The villain created by Kevin Smith would be great for an episode or two, but the fact he doesn't talk other than in onomatopoeia would not make for a good big bad.
The two names I've been hearing a lot are both female and I love the idea of the big bad being a female character. Something different from the Dark Archer, Deathstroke, Ra's al Ghul, Damien Darhk and Prometheus. The characters are Cheshire and Lady Shiva.
I think Cheshire would be a great character to bring in, but I think to do that right you need to bring back Roy Harper and Colton Haynes is part of the next Amercian Horror Story season.
Which brings us back to Lady Shiva who seems to be a lot of people's front runner at this point. Katrina Law believed she was auditioning for Shiva when she got the role of Nyssa al Ghul. Though the character more associated with Batman now, Arrow has proven it has no problems pulling from the Dark Knight. Plus her original story is tied to Richard Dragon, who was recently used as a Green Arrow villain in the comics and is very similar to the Prometheus character on the show… as opposed to the Prometheus in the comics who is VERY different. She also has ties to Green Arrow and The Question… and let's face it, everyone wants the Question to join the Arrowverse.
Shiva is a professional assassin and one of the best fighters in the DC universe. Her origin as an antagonist to Richard Dragon is she believes he killed her sister Carolyn, which isn't true. It wouldn't be hard to tie the TV version into Prometheus, his last revenge on Oliver is that he killed Shiva's sister and made it look like Green Arrow. Or they could tie her to his trip to Hong Kong in season three. There are lots of way to tie her to Oliver's past or even his parent's past.
The only hesitation I have to wards this is the show has used the highly trained female assassin trope a bit much… China White, Shado, Nyssa, Sara Lance and Talia al Ghul. Seems like Lady Shiva and even Cheshire to some extent would be somewhat similar.