We came up with the informal rules of
"only one super villain purchase per turn"
"only one kick purchase per turn"
Thus in the off chance that someone figured out a way to get unlimited power (or extremely high power) that it would only benefit them with all the cards in the lineup, one kick and one supervillain.
You don't flip over a new Super-Villain until after your turn is over. You can't purchase face down cards (yet), so there is no way to purchase more than one Super-Villain from the Super-Villain stack each turn.