YMMV / Arrow S 5 E 10 Who Are You

• Badass Decay: When Black Siren was introduced, her scream could level skyscrapers, she had CQC skills and it took an erratic frequency to finally subdue her even when against a group of vastly intelligent scientists and two heroic meta humans. Here, her scream can only hurt the ears of her opponents, and she seems to have forgotten about her combat skills. The kicker is when she got KO'd by an Action Survivor.
• Fight Scene Failure: The camera angle for Felicity punching Black Siren is horrendous, making it hard to tell that anything even happened.
• I Knew It!: Many fans had figured out that it was really Black Siren impersonating Laurel, since the creators had stubbornly insisted that they would never bring Laurel back. That and with the Lazarus Pit gone there would be really no way to bring her back, since Barry's little retcon didn't bring her back.
• Moral Event Horizon: If Prometheus didn't cross it last episode, he certainly crossed it here. Breaking out Black Siren and having her impersonate the deceased Earth-1 Laurel Lance (who was Oliver's First Love and arguably the love of his life) was downright cruel, for everyone involved, not just Oliver. Whether or not you interpret Felicity's part of hostility towards Black Siren as jealousy, it's clear that Felicity does hate her for not being their Laurel, who Felicity loved as a dear friend and wants back almost as much as Oliver does.
• Replacement Scrappy: Tina Boland, the woman who does a sonic scream in the end, who is set to become the new Black Canary is this to Black Siren, Laurel's own Earth-2 counterpart who a majority of fans want her to succeed in the mantle.