There is not a single % of alcohol that will kill the yeast. It is curve. The higher the alcohol the less viable yeast. I think it is safe to say that when you get past the 10% mark your viable yeast is getting low. They are beat up and tired.
It depends on the strain. The manufacturer will list the alcohol tolerance of each strain. Even then it isn't hard and fast, but a good idea of what a yeast is capable of.