6) Sara Lance (Arrow/Legends of Tomorrow)
Arrow is in fact full of original characters, including Thea Queen/Speedy and Tommy Merlyn. Even Felicity Smoak is basically a new character, despite the fact that she borrows the name of a very minor figure from Green Arrow comic history. The one who has made the most impact on the show and the Arrowverse as a whole, though, is Sara Lance. So much so that she has trumped a version of a classic comics character.
Sara is a slightly tricky one as both of her superhero alter egos do exist in the comics – Black Canary is obviously a long-running DC hero and White Canary is a minor villain. However, the character herself is original, so she counts here.
Trained by the League of Assassins, the highly-capable Sara was notably the first person to suit up as The Canary on the show. Her sister, (Dinah) Laurel Lance is, of course, Black Canary in the comics, but it is Sara’s version who’s almost universally preferred by the fans. Unsurprisingly, then, Sara was spun off into Legends of Tomorrow, where she gets to travel in time and space. Laurel, meanwhile, is dead.