20. Isabel Rochev
I’ll admit that the villains on Arrow have definitely proven that they know how to steal a scene. And one of those characters happens to be Isabel Rochev, played by Summer Glau.
While her time on the series was relatively short (all things considered), Isabel was a well-crafted character. One of the things that helped to increase not only our interest in the character but also Oliver Queen’s interest is just how illusive Isabel was.
For a while, it was clear that Oliver did not know what to make of this woman. He didn’t really know if she was someone he could trust (is it any shock that the answer ended up being a resounding no?), and honestly it had a lot to do with her ability to not give a lot away.
From trying to do a hostile takeover of Queen Consolidated (staged or otherwise) to actually making her allegiance to Deathstroke known, Isabel Rochev was a truly fascinating character.
I think the tragedy of Isabel’s time on Arrow is the fact that we didn’t get nearly enough of Summer Glau. Maybe the fact that they used her relatively sparingly in some cases meant that she retained her elusiveness, which was a good thing in terms of keeping the character as a fascinating and impactful addition to the series.