Define success. I think Nazi Germany did a pretty thorough job. Didn't last more than 5-10 years, depending on your measure, though.

Well, yes there were quite a few "successes". For example the whole story of World War 2 is one of ethnic cleansing. Not only the crimes of the Holocaust, but after the war there were the largest migrations and refugee waves ever seen. Germans form the East were brought to Germany, they were driven out of Czechoslovakia.

Poland, Ukraine, Belarus had a lot of ppulation exchanges. The borders were there, and now the people were moved to fit these national borders on ethnic lines.

A generation before Turkey exterminated and deported millions of minorities in Turkey. There were huge population exchanges with Greece, Armenians were murdered and deported, Assyrians and other Christians.

So anywhere where genocide due to nationalist tensions happens, you can see this policy in full effect. Success would be defined if enough of the "they" are murdered to extuingish their distinct culture.