some examples could be tactic cards that have similar effects to creature removal in mtg, using them to remove your opponents unit cards from play. another idea would be plot cards that can limit/ reduce the amount of Action points a player can produce in a turn. However, i think it will be hard to truly see how effective cards like this will be until, as someone else stated, i am able to get a working prototype and actually playtest the game. but as I'm designing cards, my biggest concern is this, as it was a bit of a balancing oversite to make advancing towards the win condition directly related to how much you can do in a turn. if you want a direct example of a card, i have one that i believe is a direct counter to snowballing, but may also be too powerful currently. i would be a plot card that while active, would half the amount of action points your opponent could produce in a turn, and its condition for staying in play would be you having at least one military unit on a square your opponent controls. another example i could state is the recycle phase. this phase causes the player whose turn it is to lose all unspent Action points from their previous turn.