Now, many fans can probably see Lena’s side in this whole conflict, and Supergirl deserves credit for showing why Lena is pulling away from Kara/Supergirl.
Given how quickly Lena and Supergirl’s relationship is falling apart and the seeming inevitability that Lena will discover Kara’s secret, we may discover that Lena will be the Season 4 big bad sooner rather than later.
Supergirl is usually more ambiguous with introducing its big bads, but that may not be necessary if the new villain is a former friend.
The show is called Supergirl, after all, and Lena’s status as a Luthor has always made it likely that the show would explore some villainous roots.