9) Cheshire
Given how many connections the villainess Cheshire has to characters and elements already on the show, it’s surprising that she has yet to appear on Arrow. A deadly mercenary, who’s trained by the League of Assassins in some versions, Jade Nguyen’s known as Cheshire due to her mask which resembles the grinning face of the Cheshire Cat from Alice in Wonderland.
If the League of Assassins connection wasn’t enough, Cheshire has also allied herself with two Arrowverse big bads on occasion – namely, Deathstroke and Vandal Savage. In Young Justice, she’s also portrayed as the sister of Artemis, who’s also on Arrow. Most notably of all, though, Cheshire is usually portrayed as a dangerous love interest for Roy Harper AKA Arsenal, in the Batman/Catwoman mold. In the comics, the pair even have a daughter, Lian.
If Colton Haynes ever returns to the show in some future season, it’d be a good opportunity to introduce Cheshire. Maybe he could just turn up on the doorstep of the Arrowcave with baby Lian?