@jrupert1@tifalockhart@mr-luxcipher: Any opinions/thoughts?

As cliche as it sounds, Thanos. He closely resembles the type of villain that works well with the dynamic of the group and the comics he's attached to are usually great. But really, they have such a varied villain gallery that any of these could fit in well.

Hmm.

Quite a variance of villainy, but if I had to choose, I'd go with Red Skull.

He's about as anathema to the ideals the JSA were founded on and stand/stood for(in a similar vein to Captain America), and has even found to means(whether it be possessing a Cosmic Cube or Professor X's brain) to pose a threat to heroes of their power-level(s).

Similar to Per Degaton and Vandal Savage in the threat he'd pose to the group as a whole.

Red Skull. The JSA used to fight Nazis.

Red Skull. JSA was pretty old school back in WWII like Alan Scott, Wildcat etc

Mephisto, has magic, and the ability to make deals, lots of potential.