The ethnic group with the largest presence in western Austria-Hungary was the Germans.
Step-by-step explanation:
The ethnic group that was dominant in the culture and politics of the Austro Hungary and also had dominance with the largest presence in western Austria-Hungary was the German population.
This was also the reason of their closer ties with Germany as there were a majority of German speaking people in these nations too.
These German ethnic gorps were also the ones that were in the position of ruling the empire of Austro Hungary and held virtually all important offices in the country.