Now that we know that Adrian Chase or Simon Morrison is Promtheus, I still want to know who Vigilante is. This is a quote from Arrow's executive producer Wendy Mericle on why they made Adrian Chase Prometheus instead of Vigilante: "One of the reasons we did do it was because everybody would be thinking, 'Of course he's going to be vigilante'. Of course Adrian Chase is Vigilante in the comic books. And we thought it would be a really fun twist to do what wwe've always done on the show, which is to take the comic book mythology and turn it on its head, and see what kind of story we can mine from a surprise like that. It was also something different for this season. We wanted to change up how we introduced the big bad and change up when we did it, how we did it, and hopefully we succeeded in that this year." One of the confirmed plotlines for season 6 stated that Vigilante's identity woiuld be revealed and it will be a familiar face, so someone we've seen before. My theory is that Captain Frank Pike is the Vigilante.
1. In the fourteenth episode of the the third season when Oliver murdered that drug dealer at Tommy Merlyn's birthday party, Pike made a note that this was community service or something like that when he, Lance, and the police arrived at the scene to investigate. That was when Lance called Laurel a gold digger (which is irrelevant to this topic by the way). Speaking of that, Pike is shown that he is willing to bend the rules to catch criminals such as when Oliver provided Pike with a USB stick containing information on Adrian Chase AKA Simon Morrison. He was willing to look into it which proves Pike is willing to bend the rules to catch criminals.
2. We never really got to see Pike and the Vigilante together. Ever since Chase stabbed Pike in that episode and sent him into a coma, Vigilante hasn't been seen. Perhaps that was another reason to why Chase stabbed him as well as trying to prevent the law from finding out he is the Throwing Star Killer.
3. When Vigilante first appeared, he tried to stop the Triad gun running deals and from their money laundering activities through Star City Trust Bank. Vigilante also went after the Spookey Crew and knew where Eric Dunn was hiding before Chase could get a warrant to have the police check the motel where Dunn was hiding. My guess is that either Vigilante has someone in the SCPD or he is someone in the SCPD. I also thought Vigilante might be Walter Steele since he is the CFO of Starling Trust Bank (which might have been renamed to Star City Trust Bank) and he has a vendetta against criminals because of everything that happened in the first season as well as Robert's yatch being sabotaged. However, in Fighting Fire With Fire, Vigilante tried to kill Oliver and he attacked Thea. Walter would never harm them.
4. In the episode Beyond Redemption, I watched how Liza Warner the corrupt police officer was fighting Team Arrow. She was in the Anti-Vigilante Task Force and Pike most likely involved in that which explains those skills that Vigilante has. Also, I recall Liza Warner's team carrying military grade weapons like a grenade. As the police captain, Pike would have access to all that equipment in the Anti-Vigilante Task Force. Also, Pike does have a motive for wanting to take things into his own hands since a lot of police officers were getting killed (such as Lance's former partner Lucas Hilton) and he felt that the law was entirely useless since the police couldn't handle the Ghosts.
5. There is a theory that Vigilante might be Dorian Chase or the real Adrian Chase. However, I don't think that he's Dorian because Amanda Westfield never mentioned having a second son when Oliver went to visit her to find out who Prometheus is (watch the clip on https://www.youtube.com/watch?v=GbxiNmPdGGE). I could be wrong, but who knows since the show is always including plot twists. I kind of hope that I'm wrong and that Vigilante is the real Adrian Chase, one who hated his father Justin Claybourne because of his corruption. Justin Claybourne was a millionaire and that can explain where Adrian got the money to finance his equipment and get the training he needs. As for Prometheus, all this time, he was just a sociopath who wanted to make Team Arrow suffer because he is thrilled. I know that Prometheus would be doing what Hunter Zolomon did by pretending to be Jay Garrick, however that would be cool. I kind of hope that they introduce that idea or that Pike is the Vigilante.