From youbastards list, we are counting Winter Soldier and Black Widow as villains as that is how they were both originally introduced in the comics.
So the other two villains would be....?
Frankly, it seems - based on the clues - that the variant figure will be a separate character altogether.
2 heroes and 4 villains PLUS a villainous troop builder. Now, theoretically you could do something like...
Black Knight II (heroic, new) with variant Black Knight I (villainous, new) or Black Widow I (villainous, redo) with variant Black Widow II (villainous, new) but putting Nick Fury/Sgt. Fury doesn't really work, and especially not with any other heroes in the wave, based on Zach's hints.
The ones in bold would be villains.