Of course, there’s also the main cast which has expanded from Oliver, Diggle, and Felicity, to include Mr. Terrific, Wild Dog, and a new Black Canary just this past season.
In its five seasons on the air so far, Arrow has seen lots of characters come and go, so there’s no shortage of potential candidates for a movie.
Assuming whether they’re alive or dead doesn’t matter, there are Oliver Queen’s parents, Malcolm Merlyn, Slade Wilson/Deathstroke, Laurel Lance, and Nyssa Al Ghul, to only name a very small number of characters.