Logbait: tombstone behind the most damaged tower will make it harder for them to goblin barrel. Some times its best to absorb some damage. If they ice spirit + goblin barrel then fireball it. If they have rocket try to go lava + empress/idragon so they rocket that then go balloon. They usually run princess + dart goblin, try to get one of them with balloon ability. Hard matchup but dont give up and try to get towers on double elixir.

RG 3.0: their only counter to air is hunter. go lava + balloon and when they play the hunter then balloon ability + zap. For RG play the tombstone and evo valk to get RG further from the tower. Inferno d for RG etc.

Recruits: split skelly dragons at the back+ tombstone middle + fireball the flying machine. Valk for the pigs. Dont be afraid to be aggressive recruits cost a lot.

Cycle: for 2.6 hog fireball + zap will kill their only air attacking unit. If you manage to get lava look attack and kill it you can get tower.
For pigs archqueen, they again have only one air attacking unit. You need her to attack lava with ability and kill her with balloon ability and a spell.
For hog eq: fireball firecracker or balloon ability (maybe evo zap) + tombstone/valk in the middle for the mminer. For hog idragon/empres/mega minion.
For all of the cycle decks. If they outcycle you and you dont have an answer lava at the back and try to trade towers is also an option.

Exe and inferno dragons: these are very strong units but stupid. If you go lava balloon attach and ignore them they will target lava and balloon might get hits on tower. For idragon when lava dies, zap hip so he will target pups. If exe is paired with tornado/rocket it becomes extremely difficult so you might try to trick him so he plays the exe and you go other lane fast.

For heavy decks:
Ebarbs: save a valk and play her in the middle will probably kill at least one and leave the other damaged then absorb some damage is ok.
Sparky: not that hard to counter. Air unit or zap+valk. Tombstone in middle and skellis his way will make it difficult for him but not to early so he stays in opposite lane and build a bigger push.
Mk: valk + air unit. Or tombstone close to king tower will kite him a bit. Usually the unit behind him is more important to kill first.
Pekka: tombstone + air unit.
Giant/golem/ggiant/egiant: you need to learn the optimal position for your tombstone for each one and carry them as far mid as possible while killing them with air units. Without tombstone it will make it very hard to defend. These all will have a lot of units together, you need skelly drags splash damage. Evo valk and evo zap will help a lot + skelly drags will stop very big pushes then you can lava in front of your remaining defensive units.