Secret identities

As a part of having an alter ego, characters try to keep secret identities, often telling as few people as possible about their alternate identity. Below are lists of characters' secret identities, and who is aware of them.

Barry Allen/The Flash

 * 1) Harrison Wells:
 * 2) Caitlin Snow:
 * 3) Cisco Ramon:
 * 4) Oliver Queen:
 * 5) Clyde Mardon :
 * 6) Joe West:

Sara Lance/The Canary

 * 1) League of Assassins: The entire League, including the likes of Ra's al Ghul, Nyssa al Ghul and Al-Owal, are aware of Sara's vigilantism in Starling City, due to her having trained with them.
 * 2) Sin: After saving her from being raped by a group of men, Sara revealed her identity to Sin.
 * 3) Oliver Queen: Oliver trapped The Canary with a bunch of ropes attached to arrows, only to take off her mask to reveal Sara. He in turn revealed his identity.
 * 4) John Diggle: When Sara joined Oliver's team, she met Diggle and Felicity.
 * 5) Felicity Smoak: When Sara joined Oliver's team, she met Felicity and Diggle.
 * 6) Quentin Lance: When the League of Assassins began to hunt Sara down, under orders from Nyssa al Ghul, Sara decided that the best way to protect her family was to reveal her secret identity, thus giving them a full idea of the dangerous situation. She revealed this to her father, who was initially shocked at her appearance, though accepting of her actions.
 * 7) Roy Harper: When Roy joined Oliver's team, he met its members, among them being Sara.
 * 8) Slade Wilson: When Slade began to hunt down Oliver and destroy him, Oliver's team fought back. In the midst of this, Slade was made aware of Sara still being alive, and further inferred Sara's vigilantism.
 * 9) Laurel Lance: When Laurel saw Sara's injuries after Slade's attack, she was nearly heartbroken on learning this.

Malcolm Merlyn/The Dark Archer

 * 1) League of Assassins: The entire league, including Ra's al Ghul, Nyssa al Ghul and Al-Owal, are aware of Malcolm's secret identity, and are all unhappy about what he'd done.
 * 2) Oliver Queen's team: Following Malcolm's reveal to The Hood about him being The Dark Archer, Oliver's entire team is aware of Malcolm's alter ego; however, they also believe him to be dead.
 * 3) Tommy Merlyn:
 * 4) Moira Queen:
 * 5) Thea Queen: As Thea was about to be attacked by one of Slade Wilson's army, Malcolm intervened and pulled off his mask to reveal his identity to her.

Oliver Queen/The Hood/The Arrow
Oliver initially acted as a vigilante known as The Hood. However, a year later he began to be known as a hero, The Arrow.
 * 1) Lodai: When Oliver returned from Lian Yu and began acting as a vigilante, he got various supplies, including his outfit and trick arrows, from Lodai. Because of this, it's assumed that Lodai knows of Oliver's secret identity.
 * 2) John Diggle: Oliver was forced to reveal his identity as The Hood when Diggle was shot by Deadshot, and had to recuperate in Oliver's base after being given medicine. Dig initially did not accept Oliver's vigilantism, but later was accepting and joined Oliver's vigilante team.
 * 3) Derek Reston: After saving his son, Derek was shot, and in his dying moments Oliver decided to reveal his identity to him, to prove that the always had his best interests at heart.
 * 4) Helena Bertinelli: After Oliver realized that Helena was The Huntress, he helped save her, and she in turn discovered The Hood's identity. Helena joined Oliver's team, helping to fight crime, however she was too blinded by her hatred for her father, and left.
 * 5) Felicity Smoak: Following Oliver being shot by Moira Queen when he tried interrogating her, he lay in the back of Felicity's car with a wound. He revealed his identity to her, and the two of them drove to Robert Queen's warehouse, where Oliver's base lay beneath. Once there, Felicity and Diggle operated on him.
 * 6) Tommy Merlyn: When his father, Malcolm, was shot by Deadshot, Oliver revealed his identity to Tommy in order to trust him to save his father's life. Tommy was conflicted over Oliver's revelation and often argued with him over his actions, though Tommy ultimately kept the secret.
 * 7) Webb: After trying to stop the production of Vertigo, Oliver was drugged with it and knocked out. He was strapped down, only to escape and kill Dr. Webb and his accomplice.
 * 8) Webb's accomplice: When Dr. Webb trapped Oliver, the two of them learnt his true identity. He was ultimately killed by Oliver when he escaped.
 * 9) Malcolm Merlyn: Oliver went after Malcolm, who revealed his identity as The Dark Archer. Malcolm ultimately won the fight, pulling off Oliver's hood in shock.
 * 10) Sara Lance: For over a year Sara suspected Oliver to be The Hood, later The Arrow, and she finally discovered that her suspicions were true when her identity was revealed to Oliver. She joined Oliver's team not long after that.
 * 11) Al-Owal: Al-Owal broke in to the Queen Mansion while Sara was staying there. Not only did he know of her whereabouts, but he also knew of Oliver's alter ego, The Arrow. It's possible he knew it due to Malcolm, his former protégé, knowing it.
 * 12) A.R.G.U.S.: The entirety of A.R.G.U.S., including the likes of Amanda Waller and Lyla Michaels, were aware of Oliver's secret identity, The Arrow, as well as his associates, John Diggle and Felicity Smoak.
 * 13) Count Vertigo: Count Vertigo was able to deduce Oliver's identity as The Arrow solely due to his large connection to Felicity Smoak, who also had a large connection to The Arrow. He used his knowledge of this connection to lure Oliver to Queen Consolidated, where Oliver confirmed his ideas of Oliver's identity, only to be killed when Count Vertigo almost killed Felicity.
 * 14) Barry Allen: Felicity and Diggle made the call to reveal Oliver's secret identity to Barry when Oliver was poisoned by unknown chemicals from an A.R.G.U.S. disaster bunker, following his fight with a Mirakuru-enhanced Cyrus Gold. Oliver was annoyed at this, though soon came to terms with it and accepted Barry.
 * 15) Slade Wilson: For the entire time that Oliver acted as The Hood, then The Arrow, Slade had figured that he was indeed Oliver, due to the green hood's significance - a reference to that of Yao Fei's and Shado's hood. He made it his sole purpose to destroy Oliver's life and reverse his heroic deeds.
 * 16) Roy Harper: Oliver was forced to reveal his secret identity to a Mirakuru-enhanced Roy in order to calm him down, to stop him from beating Ben Turner to death. Roy later joined Oliver's team, but left the team, because he blamed Oliver for Thea being kidnapped by Slade Wilson.
 * 17) Isabel Rochev: Due to being in league with Slade Wilson, a fact which she eventually revealed to Oliver, Isabel was aware of Oliver being The Arrow.
 * 18) Laurel Lance: When Slade Wilson began publicly ruining Oliver's life, he turned up at Laurel's door to tell her of Oliver's identity as The Arrow. Laurel was initially shocked and began to add up the clues, but after advice from her father, decided that it was best to not approach Oliver about it and allow him to do his job.
 * 19) Moira Queen: Whilst having a conversation about Thea, Moira also revealed to Oliver that she had figured that Oliver was the vigilante since around the events of The Undertaking, and before Oliver could say a thing, Moira expressed that she couldn't be prouder.

Slade Wilson/Deathstroke

 * 1) Sebastian Blood: After Sebastian failed to stop Oliver and Laurel from finding a file on his father, Slade became angry, killing multiple guards and pulling off his mask to reveal himself.
 * 2) Oliver Queen:
 * 3) Sara Lance:
 * 4) John Diggle:
 * 5) Felicity Smoak:
 * 6) Roy Harper:
 * 7) A.R.G.U.S.: The entirety of A.R.G.U.S., including the likes of Amanda Waller and Lyla Michaels, were not aware of Slade's secret identity, Deathstroke, until Oliver told Amanda that Slade is alive. After this she quickly figured out that the mercenary that they had codenamed Deathstroke is Slade.
 * 8) Isabel Rochev:
 * 9) Laurel Lance:
 * 10) Quentin Lance:
 * 11) League of Assassins: The entire league, including Nyssa al Ghul, are aware of Slade's secret identity; they learned this through Sara Lance.