The BALLOON, besides the X-BOW, might be the most annoying card in the game. The BALLOON does massive damage to your crown towers, and it has a decent amount of hp as well. Luckily there are a few methods you can use to easily defeat the BALLOON.
THE BEST- MINION HORDE
The MINION HORDE is a BALLOON'S worst nightmare. This card can quickly and effortlessly take out the BALLOON. Just place the card right behind the BALLOON, and the MINIONS will make quick work of it. Watch out for the opponents ARROWS or FREEZE, as these will completely put your MINIONS out of commission.
The BABY DRAGON can do some good damage to the BALLOON, but he has to be placed at the correct time. If you play this card when the BALLOON is already at your tower, it will not be able to kill the BALLOON in time. You have to play this card when the BALLOON crosses onto your side of the field.
The best thing about the INFERNO TOWER, is that it will be able to take down the BALLOON before it gets destroyed. The BALLOON will target it before your crown tower, and the potential damage that could have been done on your crown tower will be neutralized by the INFERNO TOWER.
The WIZARD can take out pretty much anything, including the BALLOON. Like the BABY DRAGON, you're going to want to place this card down before the BALLOON reaches your tower. If you do it correctly, your WIZARD will take down the BALLOON and then proceed to wreak havoc among your opponents other troops.
OTHER DECENT DEFENSES
The BALLOON can be extremely lethal when used correctly. Most people who use the BALLOON combine it with a FREEZE. When the BALLOON reaches the crown tower, wait several seconds to see if the opponent will play any troops. If they do, great, if not, great. All you have to do is place a FREEZE over everything that damages the BALLOON, and you're good to go. The BALLOON will likely destroy the crown tower before the FREEZE is up.
Another strategy is to treat the BALLOON like the PRINCE. If you keep the BALLOON "guarded" at all times by some sort of HORDE, it will take the damage for the BALLOON. Once the BALLOON makes it to the crown tower, it should be able to get off attest one hit before succumbing to enemy fire.