I think that the answer depends on how much one values the stated purpose of the Soviet Union during the time period. One of Stalin's rationales behind the expansion into the European nations, what will become known as the Eastern Bloc, was to prevent another invasion of the Soviet Union. On one hand, Stalin believed that the Soviet Union needed a zone where its own interests would be protected, states acting as a buffer and a clear line to protect his own nation. In this line of logic, there is much in way of defensive action taken in Soviet Foreign Policy.
On the other hand, the perspective from America was that this was reflective of his own paranoia and represented his own expansionist tendencies, two realities that went hand in hand with one another. Stalin's own paranoia about external threats helped to feed his own desire to appropriate more nations under his own control. This is where his foreign policy towards other nations could be seen as expansionist and more offensive than anything else.
Much of the assessment of Stalin's actions is going to be dependent on how one views the situation and through which lens, Soviet or American, one wishes to examine the actions of Stalin in regard to other nations after World War II.