There's many counters and combos against cows.
You have hard counters and then you have soft counters.
I usually play dragon slayer red on them with the AOE Fantasy Token card that comes out with a warcry. That helps a lot. It's more so a soft counter but dragon slayer red is one of the best cards in the entire game, definitely top 3 because red can half the attack and hp of any units in their cone for 10 long seconds....
The hardest counters to cows is fireball
wordle... A leveled up fireball from adventure theme will one shot them. Arrowstorm is really good too, probably better since it hits every enemy unit.
A other hard counter against them is the pigeon gang... if you level those birds to 5, I promise they will destroy those cows easily, it's 4 cost is one less than the 5 cost cows.
Lastly member berries from super heroes theme is a huge counter to cows and many units if you can learn to play it just right... Member berries will turn a fight into a win fast.