In Switzerland we have a tax when selling a house on the value it gained since you bought it. So if you buy a house for price X and you sell it for more than that, you will be taxed on the price difference. Even if the price difference is just because of market fluctuations.
This is probably a better solution against flippers, since only those making money by increasing house values are taxed. The tax can then be made more or less aggressive as needed.