I think Charlize Theron would play a good villianess. She could be like red a skull was to captain America, I stronger meaner version, have a nice fight scene between the two
Jennifer Lawrence, in my mind would be a good choice. Possibly as an up and coming hotshot supervillainess looking to take down Daddario's superheroine, one willing to take her out at all costs. Going after the people she loves and cares about, somebody really trying to get underneath Daddario's skin.
Lots of great suggestions here. I especially like Theron as an aging villainess or Lawrence as an up-and-comer (or both?). Upton comes across as more of a "goody-good girl type" IMHO, as does young Brooklyn Decker...but anything's possible with a writer of Freefall's talent, so I can't dismiss anyone.
I'd also like to recommend that Daddario have a "sidekick" (someone smaller, more vulnerable...I was going to offer Miley Cyrus but her vibe is more "bad girl" than good. Perhaps Hayden Panettiere...or any one of the CW network cuties?)